drm/amd/display: Add function prototypes to headers

Add function prototypes to headers to reduce the number of
-Wmissing-prototypes warnings.
Signed-off-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hubbub.h

@@ -133,6 +133,8 @@
 int hubbub31_init_dchub_sys_ctx(struct hubbub *hubbub,
 		struct dcn_hubbub_phys_addr_config *pa_config);
 
+void hubbub31_init(struct hubbub *hubbub);
+
 void hubbub31_construct(struct dcn20_hubbub *hubbub3,
 	struct dc_context *ctx,
 	const struct dcn_hubbub_registers *hubbub_regs,

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_hubbub.h

@@ -204,6 +204,8 @@ void hubbub32_force_usr_retraining_allow(struct hubbub *hubbub, bool allow);
 
 void hubbub32_force_wm_propagate_to_pipes(struct hubbub *hubbub);
 
+void hubbub32_init(struct hubbub *hubbub);
+
 void dcn32_program_det_size(struct hubbub *hubbub, int hubp_inst, unsigned int det_buffer_size_in_kbyte);
 
 void hubbub32_construct(struct dcn20_hubbub *hubbub2,

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_hubp.h

@@ -61,6 +61,8 @@ void hubp32_phantom_hubp_post_enable(struct hubp *hubp);
 void hubp32_cursor_set_attributes(struct hubp *hubp,
 		const struct dc_cursor_attributes *attr);
 
+void hubp32_init(struct hubp *hubp);
+
 bool hubp32_construct(
 	struct dcn20_hubp *hubp2,
 	struct dc_context *ctx,