fbdev: Fix fb_find_nearest_mode refresh comparison

Refresh rate nearness is not calculated or reset when nearest resolution
changes.

This patch resets the refresh rate differential measurement whenever a
new nearest resolution is discovered.  This fixes two error cases;
first, wherein the first mode's refresh rate differential is never
calculated and second, when the closest refresh rate from a previous
nearest resolution is erroneously preserved.
Signed-off-by: NAndrew Kephart <andrew.kephart@alereon.com>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

drivers/video/modedb.c

@@ -855,6 +855,7 @@ const struct fb_videomode *fb_find_nearest_mode(const struct fb_videomode *mode,
 			abs(cmode->yres - mode->yres);
 		if (diff > d) {
 			diff = d;
+			diff_refresh = abs(cmode->refresh - mode->refresh);
 			best = cmode;
 		} else if (diff == d) {
 			d = abs(cmode->refresh - mode->refresh);