Remove unnecessary firmware version check for gc v9_4_2

GC v9_4_2 uses a new versioning scheme for CP firmware, making
the warning ("CP firmware version too old, please update!") irrelevant.

Signed-off-by: Candice Li <candice.li@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org