.mailmap: Correct entries for Mauro Carvalho Chehab and Shuah Khan

mailmap entries may not use more than 2 email addresses per line.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>