dmaengine: nbpfaxi: Add missing check after DMA map

The DMA map functions can fail and should be tested for errors.
If the mapping fails, unmap and return an error.

Fixes: b45b262c ("dmaengine: add a driver for AMBA AXI NBPF DMAC IP cores")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Link: https://lore.kernel.org/r/20250707075752.28674-2-fourier.thomas@gmail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>