MFD: twl6040: Use resource to provide irq number for slaves

Provide the irq number for slaves via resource on the
platform device.
The irq number configuration is done in the twl6040-core
at probe time, so machine drivers do not need to be
modified.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>