In the port to 4.3, we converted to the newer irq api, but used the
chip_data for the struct aspeed_gpio pointer, rather than the
handler_data.

We use irq_set_chaned_handler_and_data to establish this pointer, which
sets handler_data. This change uses the appropriate pointer in our
handler instead.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>