gpio-mlxbf3: support valid mask

SRU Justification:

[Impact]

After syncing up the gpio-mlxbf3.c driver with the upstreamed version, we dropped the use of the valid_mask variable because kernels greater or equal to 6.2.0 dont need it.
This is no longer needed in kernel versions >= 6.2.0 because valid_mask is populated by core gpio code.
5.15 kernel doesnt support that feature so we still need to explicitly define valid_mask like we did before.
This doesnt impact the functionality of the GPIO driver but it is a security breach as it doesnt restrict the access to only gpios defined in the acpi table by valid_mask.

[Fix]

* define valid_mask and init_valid_mask

[Test Case]

* Make sure that the user (libgpiod) cannot access any other gpio besides 0->4 (gpiochip0) and 22-23 in gpiochip1.

[Regression Potential]

no known regression.