ARM: shmobile: marzen: Use INTC External IRQ pin driver for SMSC

Update the marzen board to use the INTC External IRQ pin driver for SMSC.

This code was originally posted by Magnus Damm as part of
"ARM: shmobile: INTC External IRQ pin driver on r8a7779"
but somehow omitted when I applied that patch.

Cc: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>