[SERIAL] Remove UPF_AUTOPROBE and UPF_BOOT_ONLYMCA

The functionality UPF_BOOT_ONLYMCA provided has been replaced by
the 8250_mca module, which only registers MCA ports if MCA is
present.

UPF_AUTOPROBE has no functional effect - in fact, it's never
tested.  Only ibmasm set the flag.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>