MAINTAINERS: step down as maintainer of UniPhier SoCs

I am leaving Socionext. Orphan the UniPhier platform until somebody
takes the role.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index bebe87b..101f4e1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -506,9 +506,7 @@
 F:	drivers/timer/nomadik-mtu-timer.c
 
 ARM UNIPHIER
-M:	Masahiro Yamada <yamada.masahiro@socionext.com>
-S:	Maintained
-T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-uniphier.git
+S:	Orphan (Since 2020-09)
 F:	arch/arm/mach-uniphier/
 F:	configs/uniphier_*_defconfig
 N:	uniphier