mmc: tmio: Use dma_max_mapping_size() instead of a workaround

Since the commit 133d624b

 ("dma: Introduce dma_max_mapping_size()")
provides a helper function to get the max mapping size, we can use
the function instead of the workaround code for swiotlb.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>