net: dsa: microchip: Fix error path in PTP IRQ setup

In the Linux kernel, the following vulnerability has been resolved: net: dsa: microchip: Fix error path in PTP IRQ setup If request_threaded_irq() fails during the PTP message IRQ setup, the newly created IRQ mapping is never disposed. Indeed, the ksz_ptp_irq_setup()'s error path only frees the mappings that were successfully set up. Dispose the newly created mapping if the associated request_threaded_irq() fails at setup.