drm/radeon/ni_dpm: Move 'ni_get_{pi, ps}()'s into shared header

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

drivers/gpu/drm/radeon/ni_dpm.c:727:23: warning: no previous prototype for ‘ni_get_pi’ [-Wmissing-prototypes]
727 | struct ni_power_info *ni_get_pi(struct radeon_device *rdev)
| ^~~~~~~~~
drivers/gpu/drm/radeon/ni_dpm.c:734:15: warning: no previous prototype for ‘ni_get_ps’ [-Wmissing-prototypes]
734 | struct ni_ps *ni_get_ps(struct radeon_ps *rps)
| ^~~~~~~~~

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/ni_dpm.h

···
 
 bool ni_dpm_vblank_too_short(struct radeon_device *rdev);
 
+struct ni_power_info *ni_get_pi(struct radeon_device *rdev);
+struct ni_ps *ni_get_ps(struct radeon_ps *rps);
+
 #endif

drivers/gpu/drm/radeon/si_dpm.c

···
 #include "rv770.h"
 #include "radeon.h"
 #include "radeon_asic.h"
+#include "ni_dpm.h"
 #include "si_dpm.h"
 #include "sid.h"
 
···
 };
 
 struct evergreen_power_info *evergreen_get_pi(struct radeon_device *rdev);
-struct ni_power_info *ni_get_pi(struct radeon_device *rdev);
-struct ni_ps *ni_get_ps(struct radeon_ps *rps);
 
 extern int si_mc_load_microcode(struct radeon_device *rdev);
 extern void vce_v1_0_enable_mgcg(struct radeon_device *rdev, bool enable);