drm/amdgpu: Fix warnings in amdgpu _sdma, _ucode.c

Fix below checkpatch warnings:

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
WARNING: Comparisons should place the constant on the right side of the test
WARNING: Missing a blank line after declarations

Cc: Luben Tuikov <luben.tuikov@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@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>