drm/amdgpu: Fix error & warnings in gmc_v9_0.c

drm/amdgpu: Fix error & warnings in gmc_v9_0.c

Fix below checkpatch error & warnings:

ERROR: that open brace { should be on the previous line

WARNING: static const char * array should probably be static const char * const
WARNING: Block comments use * on subsequent lines
WARNING: Block comments use a trailing */ on a separate line

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>