board: rockchip: add Powkiddy X55

The Powkiddy X55 is a Rockchip RK3566 based handheld gaming device.
UART, ADC, eMMC, and SDMMC are tested to work in U-Boot and this
successfully boots mainline Linux.

Kernel commit:
e99adc97e21a ("arm64: dts: rockchip: Add Powkiddy X55")

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/powkiddy/x55/Kconfig b/board/powkiddy/x55/Kconfig
new file mode 100644
index 0000000..a7b3ed4
--- /dev/null
+++ b/board/powkiddy/x55/Kconfig
@@ -0,0 +1,15 @@
+if TARGET_POWKIDDY_X55_RK3566
+
+config SYS_BOARD
+	default "x55"
+
+config SYS_VENDOR
+	default "powkiddy"
+
+config SYS_CONFIG_NAME
+	default "powkiddy-x55-rk3566"
+
+config BOARD_SPECIFIC_OPTIONS
+	def_bool y
+
+endif