beagle: two more GPIOs

beagle: two more GPIOs

Request two more GPIOs on Beagle:  MMC write protect, DVI enable.

Also define the first OMAP3 GPIO mux config symbols, with a new
naming convention.  Examples:

  - GPIO42 is bidirectional, and uses external pull up/down (if any);
  - GPIO42_UP is bidirectional, with an internal pullup;
  - GPIO42_DOWN is bidirectional, with an internal pulldown.
  - GPIO42_OUT is output-only, and needs no pullup or pulldown.

All of those would be fully functional through the standard GPIO
interface as well as the legacy OMAP-only one, except GPIO42_OUT
which won't let you read the actual pin value after setting it.

There's no special off-mode support for these particular pins;
on Beagle they have external pullups or pulldowns.

(OMAP2 can use this naming convention too, except that since it
has no input-enable the "_OUT" convention can't be used there.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>