Remove legacy ISA serial ports for Accent, Boca, Fourport, Hub6 and MCA
from the architecture specific serial.h include.

The only ports which remain in asm-*/serial.h are the platform specific
entries.  These should really be converted by platform maintainers to
use a platform device, such as can be found in
arch/arm/mach-footbridge/isa.c

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