This was turned from a silent confg option without a text to a normal
config option which could be selected without any other option
depending on this. This could cause the situation where REGMAP_SPI was
selected without SPI_MASTER being selected.
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36101 3c298f89-4303-0410-b956-a3cf2f4a3e73