Revert "projects/imx6/linux: reenable CONFIG_ARM_IMX6_CPUFREQ and CONFIG_REGULATOR_ANATOP support again"

This reverts commit 22cdb0e189f85b9be669a91220461a3310c47d75.
Revert "projects/*/linux: disable CONFIG_REGULATOR, this fixes #3617"

This (partialy) reverts commit 917fa5f40ea1ed08963447f2c6c230e675c58fb0.