spi: sh-msiof: Use ARCH_SHMOBILE instead of SUPERH

"spi_sh_msiof" is used on sh7723 and sh7724 only. As all of the above
select ARCH_SHMOBILE, restrict its driver dependencies from SUPERH to
ARCH_SHMOBILE.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mark Brown <broonie@kernel.org>