dma: ti: k3-udma: Fix error handling for setup_resources() in udma_probe()

In udma_probe() the return value of setup_resources() is stored in the
u32 "ch_count" member of "struct udma_dev", due to which any negative
return value which indicates an error is masked.

Fix this by storing the return value of setup_resources() in the already
declared integer variable "ret", followed by assigning it to the "ch_count"
member of "struct udma_dev" in case of no error.

While at it, change the "return ret" at the end of udma_probe() to a
"return 0", to explicitly indicate that probe was successful.

Fixes: a8837cf4 ("dma: ti: k3-udma: Query DMA channels allocated from Resource Manager")
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>