ARM: PNX4008: i2c-pnx: use the same dev_id for request_irq and free_irq

This allows i2c-pnx to free its interrupt handler when the module
is removed or if an error occurs; using the same dev_id for both
request_irq and free_irq is desirable.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Ben Dooks <ben-linux@fluff.org>