drm/radeon: Fix missing prototypes in radeon_atpx_handler.c

Fixes the following gcc with W=1:

drivers/gpu/drm/radeon/radeon_atpx_handler.c:64:6: warning: no previous prototype for ‘radeon_has_atpx’ [-Wmissing-prototypes]
64 | bool 4(void) {
| ^~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:68:6: warning: no previous prototype for ‘radeon_has_atpx_dgpu_power_cntl’ [-Wmissing-prototypes]
68 | bool radeon_has_atpx_dgpu_power_cntl(void) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:72:6: warning: no previous prototype for ‘radeon_is_atpx_hybrid’ [-Wmissing-prototypes]
72 | bool radeon_is_atpx_hybrid(void) {
| ^~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:77:6: warning: no previous prototype for ‘radeon_atpx_dgpu_req_power_for_displays’ [-Wmissing-prototypes]
77 | bool radeon_atpx_dgpu_req_power_for_displays(void) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:596:6: warning: no previous prototype for ‘radeon_register_atpx_handler’ [-Wmissing-prototypes]
596 | void radeon_register_atpx_handler(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:614:6: warning: no previous prototype for ‘radeon_unregister_atpx_handler’ [-Wmissing-prototypes]
614 | void radeon_unregister_atpx_handler(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_atpx_handler.c:159: warning: expecting prototype for radeon_atpx_validate_functions(). Prototype was for radeon_atpx_validate() instead

Cc: Christian König <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Signed-off-by: Srinivasan Shanmugam <[e-mail]>
Acked-by: Alex Deucher <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_acpi.h

···
  * BYTE  - number of active lanes
  */
 
+#if defined(CONFIG_VGA_SWITCHEROO)
+void radeon_register_atpx_handler(void);
+void radeon_unregister_atpx_handler(void);
+bool radeon_has_atpx_dgpu_power_cntl(void);
+bool radeon_is_atpx_hybrid(void);
+bool radeon_has_atpx(void);
+bool radeon_atpx_dgpu_req_power_for_displays(void);
+#endif
+
 #endif

drivers/gpu/drm/radeon/radeon_atpx_handler.c

···
 }
 
 /**
- * radeon_atpx_validate_functions - validate ATPX functions
+ * radeon_atpx_validate() - validate ATPX functions
  *
  * @atpx: radeon atpx struct
  *