efikamx: correct audio and give it a much nicer name

Smartbook audio should be wired the same way as the Smarttop, looks
like an old copy-paste problem from Babbage or something.

Rename the device from efikamx-sgtl5000 to "Efika MX Internal" as
this looks MUCH better in volume controls and improves UX (user
could never know what audio codec we use...)

Get rid of the redundant, not-used efikasb notations from the rest
of the audio driver.
smartbook: correct device tree regulators etc.

Fix spi frequency to match Smarttop (20MHz might be a bit high)

Fix regulator names - note, the same tree from Smarttop applies so
we should share this (including always-on and boot-on crap). Remove
VCAM. Dunno about RTC supply for SB, add a comment for now.

Add regulator rtc property so we get a time on Smartbook instead of
going back to 1970.