MAINTAINERS: update Shuah's email address

Update email address in MAINTAINERS file due to IT infrastructure changes
at Samsung.

Link: http://lkml.kernel.org/r/20180501212815.25911-1-shuah@kernel.org


Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>