drm/amdgpu: Fix warnings in gfxhub_ v3_0, v3_0_3.c

Fix the below checkpatch warnings:

WARNING: static const char * array should probably be static const char * const
+static const char *gfxhub_client_ids[] = {

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
+       unsigned i;

WARNING: static const char * array should probably be static const char * const
+static const char *gfxhub_client_ids[] = {

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
+       unsigned i;

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