Currently, if platform_get_irq_byname() fails, the returned error
turns into a huge value, once it is being store into a variable
of type unsigned int, hence never actually reporting any error
and causing unexpected behavior when using the values stored
in aud_drv_data->s2mm_irq and aud_drv_data->mm2s_irq.

Fix this by changing the type of variables s2mm_irq and mm2s_irq in
structure xlnx_pcm_drv_data from unsigned int to int.

Addresses-Coverity-ID: 1476096 ("Unsigned compared against 0")
Fixes: 796175a94a7f ("ASoC: xlnx: add pcm formatter platform driver")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>