MAINTAINERS: update Masahiro's email address

I have transferred to Socionext Inc.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

MAINTAINERS

@@ -159,7 +159,7 @@ F:	arch/arm/include/asm/arch-omap*/
 F:	arch/arm/include/asm/ti-common/
 
 ARM UNIPHIER
-M:	Masahiro Yamada <yamada.m@jp.panasonic.com>
+M:	Masahiro Yamada <yamada.masahiro@socionext.com>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-uniphier.git
 F:	arch/arm/mach-uniphier/