vexpress64: take over maintenance of the semi vexpress64

As agreed with Steve Rae I'm taking over maintenance of the
semihosted, emulated FVP/foundation model Versatile Express
64 bit board variant.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Steve Rae <srae@broadcom.com>

board/armltd/vexpress64/MAINTAINERS

@@ -6,6 +6,6 @@ F:	include/configs/vexpress_aemv8a.h
 F:	configs/vexpress_aemv8a_defconfig
 
 VEXPRESS_AEMV8A_SEMI BOARD
-M:	Steve Rae <srae@broadcom.com>
+M:	Linus Walleij <linus.walleij@linaro.org>
 S:	Maintained
 F:	configs/vexpress_aemv8a_semi_defconfig