sun6i: Add LCD display support for MSI Primo81 tablet

The MSI Primo81 tablet has B079XAN01/LP079X01 7.85" 768x1024 IPS
MIPI display, connected to the parallel LCD interface via SSD2828
bridge chip. The panel has 18-bit color depth and needs dithering,
in spite of having RGB data delivered from A31s to SSD2828 using
24-bit arrangement.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

configs/MSI_Primo81_defconfig

@@ -10,6 +10,16 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS=""
 CONFIG_FDTFILE="sun6i-a31s-primo81.dtb"
+CONFIG_VIDEO_LCD_MODE="x:768,y:1024,depth:18,pclk_khz:66000,le:56,ri:60,up:30,lo:36,hs:64,vs:50,sync:3,vmode:0"
+CONFIG_VIDEO_LCD_PANEL_MIPI_4_LANE_513_MBPS_VIA_SSD2828=y
+CONFIG_VIDEO_LCD_SSD2828_TX_CLK=27
+CONFIG_VIDEO_LCD_SSD2828_RESET="PA26"
+CONFIG_VIDEO_LCD_SPI_CS="PH9"
+CONFIG_VIDEO_LCD_SPI_SCLK="PH10"
+CONFIG_VIDEO_LCD_SPI_MOSI="PH11"
+CONFIG_VIDEO_LCD_SPI_MISO="PH12"
+CONFIG_VIDEO_LCD_BL_EN="PA25"
+CONFIG_VIDEO_LCD_BL_PWM="PH13"
 CONFIG_USB_KEYBOARD=n
 +S:CONFIG_ARM=y
 +S:CONFIG_ARCH_SUNXI=y