Big MMC init clean up:

- Remove enabled field from slots. It is really intended to mean enabled controller,
  not enabled slot. Some controllers can have multiple multiplexed slots connected
  to the first controller, such as H4 and N8X0.

- Initialize MMC devices dynamically as suggested by Russell King

- Fix omap1 mmc clock instance numbers

- Also attempt to fix massive omap1 MMC breakage caused by patch
  138ab9f8. Remove obviously broken
  MMC configurations for now. MMC is still not working for any
  omap1 boards.
Signed-off-by: Tony Lindgren <tony@atomide.com>