[PATCH] Serial: Convert 8250 revision-based bug fixes to bug bitmask

For some 8250 port types, we used to check the type of the port, and
then determine whether the chip revision means the device is buggy.
Instead, introduce a bit array, and set the appropriate bit(s) when
we discover a buggy device.

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