Revert "serial: max310x: Fix build error"

This reverts commit e3c6ea9b as it
didn't help anything, and caused more problems than expected.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>