dmaengine: sh: rz-dmac: handle configs where one address is zero

Configs like the ones coming from the MMC subsystem will have either
'src' or 'dst' zeroed, resulting in an unknown bus width. This will bail
out on the RZ DMA driver because of the sanity check for a valid bus
width. Reorder the code, so that the check will only be applied when the
corresponding address is non-zero.

Fixes: 5000d370 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://lore.kernel.org/r/20241007110200.43166-6-wsa+renesas@sang-engineering.com


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