arm: rockchip: Fix typo in ROCKCHIP_RK3288 help

UART,s -> UARTs, to avoid this spreading via copy&paste.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index 8a5d62a..5c4a4c2 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -21,7 +21,7 @@
 	  including NEON and GPU, 1MB L2 cache, Mali-T7 graphics, two
 	  video interfaces supporting HDMI and eDP, several DDR3 options
 	  and video codec support. Peripherals include Gigabit Ethernet,
-	  USB2 host and OTG, SDIO, I2S, UART,s, SPI, I2C and PWMs.
+	  USB2 host and OTG, SDIO, I2S, UARTs, SPI, I2C and PWMs.
 
 config ROCKCHIP_RK3399
 	bool "Support Rockchip RK3399"