net: ti: icssg-prueth: Fix signedness bug in prueth_init_rx_chns()

The rx_chn->irq[] array is unsigned int but it should be signed for the
error handling to work.  Also if k3_udma_glue_rx_get_irq() returns zero
then we should return -ENXIO instead of success.

Fixes: 128d5874

 ("net: ti: icssg-prueth: Add ICSSG ethernet driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://lore.kernel.org/r/05282415-e7f4-42f3-99f8-32fde8f30936@moroto.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>