m68knommu: use IRQF_DISABLE in m68328serial.c

Use IRQF_DISABLED instead of obsolete IRQ_FLG_STD for request_irq() flags
in m68328serial.c driver.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>