ARM: ep93xx: convert vision_ep9307 to MULTI_IRQ_HANDLER

As done for the other ep93xx machines in:

commit 9a6879bd
ARM: ep93xx: convert to MULTI_IRQ_HANDLER

Now that there is a generic IRQ handler for multiple VIC devices use it
for vision_ep9307 to help building multi platform kernels.

Signed-off-by: Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ryan Mallon <rmallon@gmail.com>
Reviewed-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>