spi: tegra: checking for ERR_PTR instead of NULL
spi: tegra: checking for ERR_PTR instead of NULL

dma_request_slave_channel() returns NULL on error and not ERR_PTRs.
I've fixed this by using dma_request_slave_channel_reason() which does
return ERR_PTRs.

Fixes: a915d150f68d ('spi: tegra: convert to standard DMA DT bindings')
Signed-off-by: Dan Carpenter <ff341aa343d564f9e53e9dcb6996be8c04859a66@oracle.com>
Signed-off-by: Stephen Warren <5ef2a23ba3aff51d1cfc8c113c1ec34b608b3b13@nvidia.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs