drm/amdgpu: rename smumgr to smum for dpm

Rename smumgr.h to smum.h, because smum.h is to align with the dpm of
other chips and we will use "iceland_smumgr" at powerplay in following
patches.

Signed-off-by: Huang Rui <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/iceland_dpm.c

···
 #include <linux/firmware.h>
 #include "drmP.h"
 #include "amdgpu.h"
-#include "iceland_smumgr.h"
+#include "iceland_smum.h"
 
 MODULE_FIRMWARE("amdgpu/topaz_smc.bin");
 

drivers/gpu/drm/amd/amdgpu/iceland_smc.c

···
 #include "drmP.h"
 #include "amdgpu.h"
 #include "ppsmc.h"
-#include "iceland_smumgr.h"
+#include "iceland_smum.h"
 #include "smu_ucode_xfer_vi.h"
 #include "amdgpu_ucode.h"