MAINTAINERS: Fix uniphier-mdmac.c file path

Commit 32e74aab ("dmaengine: uniphier-mdmac: add UniPhier MIO DMAC
driver") wrongly put filepath for uniphier-mdmac.c, fix it

Fixes: 32e74aab ("dmaengine: uniphier-mdmac: add UniPhier MIO DMAC driver")
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>