regulator: Use menuconfig in Kconfig

Use menuconfig instead of flat configs so that you can disable/enable
regulator items with one selection.  Also, use depends instead of
reverse selections to make life easier, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>