NFC: pn544_i2c: Fix null pointer exception when not using platform data

Fixes a null pointer exception occurring when the IRQ request in
pn544_hci_i2c_probe fails and no platform data is available.

Signed-off-by: Clément Perrochaud <clement.perrochaud@nxp.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>