drm/amd/amdgpu: Fix style errors in amdgpu_drv.c & amdgpu_device.c

Fix following checkpatch style errors in amdgpu_drv.c &
amdgpu_device.c

ERROR: exactly one space required after that #ifdef
ERROR: spaces required around that '+=' (ctx:WxV)
ERROR: space required before the open brace '{'
ERROR: spaces required around that '||' (ctx:VxE)
ERROR: space prohibited before that close parenthesis ')'
ERROR: space required before the open parenthesis '('
ERROR: space required before the open brace '{'
ERROR: code indent should use tabs where possible

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