ethernet/ti: delete if NULL check befort devm_kfree

devm_kfree check the pointer, there is no need to check before
devm_kfree call.
This change is to cleanup the code a bit.

Signed-off-by: Bernard Zhao <bernard@vivo.com>
Link: https://lore.kernel.org/r/20220516015208.6526-1-bernard@vivo.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>