drm/panel: abt-y030xx067a: yellow tint fix

The previous parameters caused an unbalanced yellow tint.

Fixes: 7467389bdafb ("drm/panel: Add ABT Y030XX067A 3.0" 320x480 panel")
Signed-off-by: Christophe Branchereau <[e-mail]>
Acked-by: Sam Ravnborg <[e-mail]>
[Paul: Add Fixes: tag, and fix case and punctuation in commit message]
Signed-off-by: Paul Cercueil <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Maarten Lankhorst <[e-mail]>

drivers/gpu/drm/panel/panel-abt-y030xx067a.c

···
 	{ 0x09, REG09_SUB_BRIGHT_R(0x20) },
 	{ 0x0a, REG0A_SUB_BRIGHT_B(0x20) },
 	{ 0x0b, REG0B_HD_FREERUN | REG0B_VD_FREERUN },
-	{ 0x0c, REG0C_CONTRAST_R(0x10) },
-	{ 0x0d, REG0D_CONTRAST_G(0x10) },
+	{ 0x0c, REG0C_CONTRAST_R(0x00) },
+	{ 0x0d, REG0D_CONTRAST_G(0x00) },
 	{ 0x0e, REG0E_CONTRAST_B(0x10) },
 	{ 0x0f, 0 },
 	{ 0x10, REG10_BRIGHT(0x7f) },