The DMA address returned by dma_map_single() should be checked with
dma_mapping_error(). Fix the ps3stor_setup() function accordingly.

Fixes: 80071802 ("[POWERPC] PS3: Storage Driver Core")
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201213182622.23047-1-vincent.stehle@laposte.net