staging: goldfish: Call free_irq in error path

If misc_register failed in goldfish_audio_probe, the already requested
IRQ wouldn't get freed. Add a call to free_irq() like there is in
goldfish_audio_remove().

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>