m68k/atari: Change VME irq numbers from unsigned long to unsigned int

Device interrupts numbers were changed to unsigned int in 1997, the year
IRQ_MACHSPEC was killed as well.

Also kill a related cast while we're at it.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: netdev@vger.kernel.org