spi: sh-msiof: Use devm_platform_ioremap_resource() helper

Use the devm_platform_ioremap_resource() helper instead of open-coding
the same operation.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20190807085213.24666-1-geert+renesas@glider.be


Signed-off-by: Mark Brown <broonie@kernel.org>