drm/amdgpu: Remove unreachable code in 'atom_skip_src_int()'

Fixes the below:
drivers/gpu/drm/amd/amdgpu/atom.c:398 atom_skip_src_int() warn: ignoring unreachable code.

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