fib_tests.sh/fib-onlink-tests.sh in net of ubuntu_kernel_selftests failed on F-ibm-5.4 (Error: Unknown device type)

Issue found on Focal ibm 5.4.0-1007.8

Test failed with:
# Error: Unknown device type.

# selftests: net: fib_tests.sh
#
# Single path route test
# Start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# Nexthop device deleted
# TEST: IPv4 fibmatch - no route [ OK ]
# TEST: IPv6 fibmatch - no route [ OK ]
#
# Multipath route test
# Start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# One nexthop device deleted
# TEST: IPv4 - multipath route removed on delete [ OK ]
# TEST: IPv6 - multipath down to single path [ OK ]
# Second nexthop device deleted
# TEST: IPv6 - no route [ OK ]
#
# Single path, admin down
# Start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# Route deleted on down
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
#
# Admin down multipath
# Verify start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# One device down, one up
# TEST: IPv4 fibmatch on down device [ OK ]
# TEST: IPv6 fibmatch on down device [ OK ]
# TEST: IPv4 fibmatch on up device [ OK ]
# TEST: IPv6 fibmatch on up device [ OK ]
# TEST: IPv4 flags on down device [ OK ]
# TEST: IPv6 flags on down device [ OK ]
# TEST: IPv4 flags on up device [ OK ]
# TEST: IPv6 flags on up device [ OK ]
# Other device down and up
# TEST: IPv4 fibmatch on down device [ OK ]
# TEST: IPv6 fibmatch on down device [ OK ]
# TEST: IPv4 fibmatch on up device [ OK ]
# TEST: IPv6 fibmatch on up device [ OK ]
# TEST: IPv4 flags on down device [ OK ]
# TEST: IPv6 flags on down device [ OK ]
# TEST: IPv4 flags on up device [ OK ]
# TEST: IPv6 flags on up device [ OK ]
# Both devices down
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
#
# Local carrier tests - single path
# Start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 - no linkdown flag [ OK ]
# TEST: IPv6 - no linkdown flag [ OK ]
# Carrier off on nexthop
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 - linkdown flag set [ OK ]
# TEST: IPv6 - linkdown flag set [ OK ]
# Route to local address with carrier down
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 linkdown flag set [ OK ]
# TEST: IPv6 linkdown flag set [ OK ]
#
# Single path route carrier test
# Start point
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 no linkdown flag [ OK ]
# TEST: IPv6 no linkdown flag [ OK ]
# Carrier down
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 linkdown flag set [ OK ]
# TEST: IPv6 linkdown flag set [ OK ]
# Second address added with carrier down
# TEST: IPv4 fibmatch [ OK ]
# TEST: IPv6 fibmatch [ OK ]
# TEST: IPv4 linkdown flag set [ OK ]
# TEST: IPv6 linkdown flag set [ OK ]
# Error: Unknown device type.
not ok 14 selftests: net: fib_tests.sh # exit=2

This is failing with 5.4.0-1006 as well. So this is not a regression.