Introduce support for board specific group assignments of TWL4030
power resources.  The resource type and type2 fields can also be
specified.

Most such power resources are regulators; this hook can be used
to ensure regulators that will never be used get properly disabled,
regardless of what the bootloader does.  Other resources include
control signals like CLKREQ and REGEN; this can properly couple
TWL CLKREQ (out) to OMAP SYSCLK_REQ (in) so retention mode works.

[ dbrownell@users.sourceforge.net: cosmetic and doc updates;
  use the RES_* constants in the regulator driver; fix buildbug ]
Signed-off-by: Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>