[ldv-project] prism54: fix checks for dma mapping errors

[Kalle Valo]

> prism54 checks for dma mapping errors by comparison returned address
> with zero, while pci_dma_mapping_error() should be used.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshilov at ispras.ru>

Thanks, applied to wireless-drivers-next.git.

Kalle Valo