MAINTAINERS: Update Mun Yew Tham as Altera Mailbox Driver maintainer

Update Altera Mailbox Driver maintainer's email from <joyce.ooi@intel.com> to <mun.yew.tham@intel.com>

Signed-off-by: Mun Yew Tham <mun.yew.tham@intel.com>
Acked-by: Joyce Ooi <joyce.ooi@intel.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

MAINTAINERS

@@ -798,7 +798,7 @@ F:	Documentation/devicetree/bindings/i2c/i2c-altera.txt
 F:	drivers/i2c/busses/i2c-altera.c
 
 ALTERA MAILBOX DRIVER
-M:	Joyce Ooi <joyce.ooi@intel.com>
+M:	Mun Yew Tham <mun.yew.tham@intel.com>
 S:	Maintained
 F:	drivers/mailbox/mailbox-altera.c