fbdev: riva: Use backlight helper

Instead of retrieving the backlight brightness in struct
backlight_properties manually, and then checking whether the backlight
should be on at all, use backlight_get_brightness() which does all
this and insulates this from future changes.

Signed-off-by: Stephen Kitt <[e-mail]>
Cc: Antonino Daplas <[e-mail]>
Cc: Helge Deller <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Reviewed-by: Daniel Thompson <[e-mail]>
Signed-off-by: Helge Deller <[e-mail]>

drivers/video/fbdev/riva/fbdev.c

···
 {
 	struct riva_par *par = bl_get_data(bd);
 	U032 tmp_pcrt, tmp_pmc;
-	int level;
-
-	if (bd->props.power != FB_BLANK_UNBLANK ||
-	    bd->props.fb_blank != FB_BLANK_UNBLANK)
-		level = 0;
-	else
-		level = bd->props.brightness;
+	int level = backlight_get_brightness(bd);
 
 	tmp_pmc = NV_RD32(par->riva.PMC, 0x10F0) & 0x0000FFFF;
 	tmp_pcrt = NV_RD32(par->riva.PCRTC0, 0x081C) & 0xFFFFFFFC;