drm/amdgpu: add the argument description for gpu_addr

drm/amdgpu: add the argument description for gpu_addr

Add argument description for the input argument
gpu_addr for amdgpu_seq64_alloc.

Fixes the warning raised by the compiler:
drivers/gpu/drm/amd/amdgpu/amdgpu_seq64.c:168:
warning: Function parameter or struct member 'gpu_addr' not described in 'amdgpu_seq64_alloc

Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>