Revert "sc16is7xx: implemented get_mctrl"

This reverts commit a3f0b77f.

Maarten writes:
	It appears to be wrong and I don't have a good idea how to fix
	it yet.

Cc: Maarten Brock <m.brock@vanmierlo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>