drm/amdgpu: fix ras parameter descriptions

The descriptions of modinfo wrongly show two parameters
for each feature(see below). This patch can fix this
incorrect outputs.

parm:           amdgpu_ras_enable:Enable RAS features on the GPU (0 = disable, 1 = enable, -1 = auto (default))
parm:           ras_enable:int
parm:           amdgpu_ras_mask:Mask of RAS features to enable (default 0xffffffff), only valid when ras_enable == 1
parm:           ras_mask:uint

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: xinhui pan <xinhui.pan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>