serial: pic32_uart: Fix double free of 'sport->irq_fault_name'.

Allocated memory for 'sport->irq_fault_name' is freed twice, first
in error check of 'if(!sport->irq_rx_name)' and other in fallback
handler.

Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>