rockchip: MAINTAINERS: fix board name for Radxa ROCK 4C+

align with other ROCK series.

Fixes: 2b506407c8 ("rockchip: Add MAINTAINERS entry for Radxa Rock 4C+")
Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/rockchip/evb_rk3399/MAINTAINERS b/board/rockchip/evb_rk3399/MAINTAINERS
index cb44bc9..c7e412b 100644
--- a/board/rockchip/evb_rk3399/MAINTAINERS
+++ b/board/rockchip/evb_rk3399/MAINTAINERS
@@ -80,7 +80,7 @@
 F:	arch/arm/dts/rk3399-u-boot.dtsi
 F:	arch/arm/dts/rk3399-orangepi-u-boot.dtsi
 
-RADXA ROCK 4C+
+ROCK-4C+
 M:	FUKAUMI Naoki <naoki@radxa.com>
 S:	Maintained
 F:	configs/rock-4c-plus-rk3399_defconfig