MAINTAINERS: update Xiubo's email address

My current email address will be gone shortly, update my email to be a
gmail one.

Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
Cc: Timur Tabi <timur@tabi.org>
Cc: Takashi Iwai <tiwai@suse.de>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -4037,7 +4037,7 @@ F:	drivers/tty/serial/ucc_uart.c
 FREESCALE SOC SOUND DRIVERS
 M:	Timur Tabi <timur@tabi.org>
 M:	Nicolin Chen <nicoleotsuka@gmail.com>
-M:	Xiubo Li <Li.Xiubo@freescale.com>
+M:	Xiubo Li <Xiubo.Lee@gmail.com>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
 L:	linuxppc-dev@lists.ozlabs.org
 S:	Maintained