drm/sun4i: Move rate variables to long long

Our clock rate variables are getting pretty close to the LONG_MAX / ULONG_MAX
limit, especially since we will start doing arithmetic on it. Move those
types to unsigned long long to be sure we don't overflow their type.
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com> # tested on pinebook
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/022c3b850413edd6afbca20062f100971de2f5af.1551191081.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun4i_rgb.c

@@ -60,8 +60,8 @@ static enum drm_mode_status sun4i_rgb_mode_valid(struct drm_encoder *crtc,
 	struct sun4i_tcon *tcon = rgb->tcon;
 	u32 hsync = mode->hsync_end - mode->hsync_start;
 	u32 vsync = mode->vsync_end - mode->vsync_start;
-	unsigned long rate = mode->clock * 1000;
-	long rounded_rate;
+	unsigned long long rate = mode->clock * 1000;
+	unsigned long long rounded_rate;
 
 	DRM_DEBUG_DRIVER("Validating modes...\n");