gpio/pca953x: Use handle_simple_irq instead of handle_edge_irq

Make pca953x driver use the simple irq handler since no hardware control
is necessary and the driver lacks an irq_ack function. handle_edge_irq()
calls chip->irq_ack() which crashes since this function does not exist.

Signed-off-by: Erik Botö <erik.boto@pelagicore.com>
Signed-off-by: Richard Röjfors <richard.rojfors@pelagicore.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>