drivers/misc/fsl_law.c: Rearrange code to avoid duplication

The current code redefines functions based on FSL_CORENET_ vs not -
create macros/inlines instead that hide the differences.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>