drm/amd/amdgpu: add prefix for pr_* prints

amdgpu uses lots of pr_* calls for printing error messages.
With this prefix, errors shall be more obvious to the end
use regarding its origin, and may help debugging.

Prefix format:

[xxx.xxxxx] amdgpu: ...
Signed-off-by: Aurabindo Pillai <mail@aurabindo.in>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -28,6 +28,12 @@
 #ifndef __AMDGPU_H__
 #define __AMDGPU_H__
 
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) "amdgpu: " fmt
+
 #include "amdgpu_ctx.h"
 
 #include <linux/atomic.h>