drm/amd/amdgpu: Fix warnings in amdgpu_encoders.c

Fix below checkpatch warnings:

WARNING: Missing a blank line after declarations
+                       struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(connector);
+                       amdgpu_encoder->active_device = amdgpu_encoder->devices & amdgpu_connector->devices;

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

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