drm/radeon/r600: Move 'evergreen_rlc_resume()'s prototype to shared header

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

 drivers/gpu/drm/radeon/evergreen.c:4380:5: warning: no previous prototype for ‘evergreen_rlc_resume’ [-Wmissing-prototypes]
 4380 | int evergreen_rlc_resume(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

@@ -46,5 +46,6 @@ 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);
+int evergreen_rlc_resume(struct radeon_device *rdev);
 
 #endif				/* __RADEON_EVERGREEN_H__ */

drivers/gpu/drm/radeon/r600.c

@@ -39,6 +39,7 @@
 
 #include "atom.h"
 #include "avivod.h"
+#include "evergreen.h"
 #include "r600.h"
 #include "r600d.h"
 #include "rv770.h"
@@ -113,7 +114,6 @@ static void r600_gpu_init(struct radeon_device *rdev);
 void r600_fini(struct radeon_device *rdev);
 void r600_irq_disable(struct radeon_device *rdev);
 static void r600_pcie_gen2_enable(struct radeon_device *rdev);
-extern int evergreen_rlc_resume(struct radeon_device *rdev);
 
 /*
  * Indirect registers accessor