drm:dcn31: fix boolreturn.cocci warnings

./drivers/gpu/drm/amd/display/dc/dcn31/dcn31_panel_cntl.c:112:9-10:WARNING:
return of 0/1 in function 'dcn31_is_panel_backlight_on'
with return type bool

./drivers/gpu/drm/amd/display/dc/dcn31/dcn31_panel_cntl.c:122:9-10:WARNING:
return of 0/1 in function 'dcn31_is_panel_powered_on'
with return type bool

Return statements in functions returning bool should use true/false
instead of 1/0.

Generated by: scripts/coccinelle/misc/boolreturn.cocci

Reported-by: Zeal Robot <[e-mail]>
Signed-off-by: Jing Yangyang <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_panel_cntl.c

···
 	union dmub_rb_cmd cmd;
 
 	if (!dcn31_query_backlight_info(panel_cntl, &cmd))
-		return 0;
+		return false;
 
 	return cmd.panel_cntl.data.is_backlight_on;
 }
···
 	union dmub_rb_cmd cmd;
 
 	if (!dcn31_query_backlight_info(panel_cntl, &cmd))
-		return 0;
+		return false;
 
 	return cmd.panel_cntl.data.is_powered_on;
 }