drm/radeon/evergreen: Move 'cik_*()'s prototypes to shared header

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

 drivers/gpu/drm/radeon/cik.c:6413:6: warning: no previous prototype for ‘cik_init_cp_pg_table’ [-Wmissing-prototypes]
 6413 | void cik_init_cp_pg_table(struct radeon_device *rdev)
 | ^~~~~~~~~~~~~~~~~~~~
 drivers/gpu/drm/radeon/cik.c:6670:5: warning: no previous prototype for ‘cik_get_csb_size’ [-Wmissing-prototypes]
 6670 | u32 cik_get_csb_size(struct radeon_device *rdev)
 | ^~~~~~~~~~~~~~~~
 drivers/gpu/drm/radeon/cik.c:6702:6: warning: no previous prototype for ‘cik_get_csb_buffer’ [-Wmissing-prototypes]
 6702 | void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer)
 | ^~~~~~~~~~~~~~~~~~

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/cik.h

@@ -30,5 +30,8 @@ void cik_exit_rlc_safe_mode(struct radeon_device *rdev);
 int ci_mc_load_microcode(struct radeon_device *rdev);
 void cik_update_cg(struct radeon_device *rdev, u32 block, bool enable);
 u32 cik_gpu_check_soft_reset(struct radeon_device *rdev);
+void cik_init_cp_pg_table(struct radeon_device *rdev);
+u32 cik_get_csb_size(struct radeon_device *rdev);
+void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 
 #endif                         /* __CIK_H__ */

drivers/gpu/drm/radeon/evergreen.c

@@ -31,6 +31,7 @@
 
 #include "atom.h"
 #include "avivod.h"
+#include "cik.h"
 #include "ni.h"
 #include "rv770.h"
 #include "evergreen.h"
@@ -217,10 +218,6 @@ static void evergreen_gpu_init(struct radeon_device *rdev);
 void evergreen_fini(struct radeon_device *rdev);
 void evergreen_pcie_gen2_enable(struct radeon_device *rdev);
 void evergreen_program_aspm(struct radeon_device *rdev);
-void cik_init_cp_pg_table(struct radeon_device *rdev);
-
-extern u32 cik_get_csb_size(struct radeon_device *rdev);
-extern void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 
 static const u32 evergreen_golden_registers[] =
 {