drm/amd/display: Remove MALL function from DCN3.1

[why]
DCN31 doesn't have MALL in DMUB so to avoid sending unknown commands to
DMUB just remove the function pointer.

[how]
Remove apply_idle_power_optimizations from function pointers structure
for DCN31

Reviewed-by: Nicholas Kazlauskas <[e-mail]>
Acked-by: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Mikita Lipski <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_init.c

···
 	.set_flip_control_gsl = dcn20_set_flip_control_gsl,
 	.get_vupdate_offset_from_vsync = dcn10_get_vupdate_offset_from_vsync,
 	.calc_vupdate_position = dcn10_calc_vupdate_position,
-	.apply_idle_power_optimizations = dcn30_apply_idle_power_optimizations,
 	.set_backlight_level = dcn21_set_backlight_level,
 	.set_abm_immediate_disable = dcn21_set_abm_immediate_disable,
 	.set_pipe = dcn21_set_pipe,