drm/amd/display: remove unused struct 'dc_reg_sequence'

'dc_reg_sequence' was added in
commit 44788bbc309b ("drm/amd/display: refactor reg_update")

but isn't actually used.

Remove it.

Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dc_helper.c

···
 	uint32_t mask;
 };
 
-struct dc_reg_sequence {
-	uint32_t addr;
-	struct dc_reg_value_masks value_masks;
-};
-
 static inline void set_reg_field_value_masks(
 	struct dc_reg_value_masks *field_value_mask,
 	uint32_t value,