i2c-pxa2xx: add support for shared IRQ handler

Sodaville has three of them on a single IRQ. IRQF_DISABLED is removed
because it is a NOP allready and scheduled for removal.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>