m68k: Remove deprecated IRQF_DISABLED

This patch proposes to remove the IRQF_DISABLED flag from m68k architecture
code. It's a NOOP since 2.6.35 and it will be removed one day.

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>