drm/radeon/evergreen_dma: Move 'evergreen_gpu_check_soft_reset()'s prototype to shared header

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/radeon/evergreen.c:3825:5: warning: no previous prototype for ‘evergreen_gpu_check_soft_reset’ [-Wmissing-prototypes]
 3825 | u32 evergreen_gpu_check_soft_reset(struct radeon_device *rdev)
 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/evergreen.h

@@ -45,5 +45,6 @@ int sumo_rlc_init(struct radeon_device *rdev);
 void evergreen_gpu_pci_config_reset(struct radeon_device *rdev);
 u32 evergreen_get_number_of_dram_channels(struct radeon_device *rdev);
 void evergreen_print_gpu_status_regs(struct radeon_device *rdev);
+u32 evergreen_gpu_check_soft_reset(struct radeon_device *rdev);
 
 #endif				/* __RADEON_EVERGREEN_H__ */

drivers/gpu/drm/radeon/evergreen_dma.c

@@ -24,10 +24,9 @@
 
 #include "radeon.h"
 #include "radeon_asic.h"
+#include "evergreen.h"
 #include "evergreend.h"
 
-u32 evergreen_gpu_check_soft_reset(struct radeon_device *rdev);
-
 /**
  * evergreen_dma_fence_ring_emit - emit a fence on the DMA ring
  *