drm/amdgpu: Use min_t to replace min

Use min_t to replace min, min_t is a bit fast because min use
twice typeof.

And using min_t is cleaner here since the min/max macros
do a typecheck while min_t()/max_t() to an explicit type cast.

Fixes the below checkpatch warning:

WARNING: min() should probably be min_t()

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@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>