drm: ssd130x: Fix COM scan direction register mask

The SSD130x's command to toggle COM scan direction uses bit 3 and only
bit 3 to set the direction of the scanout. The driver has an incorrect
GENMASK(3, 2), causing the setting to be set on bit 2, rendering it
ineffective.

Fix the mask to only bit 3, so that the requested setting is applied
correctly.

Fixes: a61732e8 ("drm: Add driver for Solomon SSD130x OLED displays")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220308160758.26060-1-wens@kernel.org

drivers/gpu/drm/solomon/ssd130x.c

@@ -61,7 +61,7 @@
 #define SSD130X_SET_COM_PINS_CONFIG		0xda
 #define SSD130X_SET_VCOMH			0xdb
 
-#define SSD130X_SET_COM_SCAN_DIR_MASK		GENMASK(3, 2)
+#define SSD130X_SET_COM_SCAN_DIR_MASK		GENMASK(3, 3)
 #define SSD130X_SET_COM_SCAN_DIR_SET(val)	FIELD_PREP(SSD130X_SET_COM_SCAN_DIR_MASK, (val))
 #define SSD130X_SET_CLOCK_DIV_MASK		GENMASK(3, 0)
 #define SSD130X_SET_CLOCK_DIV_SET(val)		FIELD_PREP(SSD130X_SET_CLOCK_DIV_MASK, (val))