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

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

drivers/gpu/drm/radeon/si.c:5678:5: warning: no previous prototype for ‘si_get_csb_size’ [-Wmissing-prototypes]
5678 | u32 si_get_csb_size(struct radeon_device *rdev)
| ^~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/si.c:5710:6: warning: no previous prototype for ‘si_get_csb_buffer’ [-Wmissing-prototypes]
5710 | void si_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer)
| ^~~~~~~~~~~~~~~~~

Cc: Alex Deucher <[e-mail]>
Cc: "Christian König" <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/evergreen.c

···
 #include "radeon_asic.h"
 #include "radeon_audio.h"
 #include "radeon_ucode.h"
+#include "si.h"
 
 #define DC_HPDx_CONTROL(x)        (DC_HPD1_CONTROL     + (x * 0xc))
 #define DC_HPDx_INT_CONTROL(x)    (DC_HPD1_INT_CONTROL + (x * 0xc))
···
 void evergreen_program_aspm(struct radeon_device *rdev);
 void cik_init_cp_pg_table(struct radeon_device *rdev);
 
-extern u32 si_get_csb_size(struct radeon_device *rdev);
-extern void si_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 extern u32 cik_get_csb_size(struct radeon_device *rdev);
 extern void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 

drivers/gpu/drm/radeon/si.h

···
 void si_vram_gtt_location(struct radeon_device *rdev, struct radeon_mc *mc);
 void si_rlc_reset(struct radeon_device *rdev);
 void si_init_uvd_internal_cg(struct radeon_device *rdev);
+u32 si_get_csb_size(struct radeon_device *rdev);
+void si_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 
 #endif                         /* __SI_H__ */