twl4030_charger: allow full range of current selection.

To allow charging with more than 850mA we need to set CGAIN.
This affect several other thresholds so they need to be
adjusted to match.

CGAIN can not be changed while charging is active.
So we disable charging while we update the max current.

Signed-off-by: NeilBrown <neilb@suse.de>
twl4030_charger: add ac/mode to match usb/mode

This allows AC charging to be turned off, must like usb charging.

No support for linear (aka continuous) charging from 'ac' yet.

Signed-off-by: NeilBrown <neilb@suse.de>
twl4030_charger: move 'max_current' to each power supply.

Now both twl4030_ac and twl4030_usb have their own max_current.

Values written to ac/max_current persist.
Values written to usb/max_current only persist until an usb
plug/unplug event at which point it reverts to default.

Signed-off-by: NeilBrown <neilb@suse.de>
GTA04: only enabled 1GHz if chip supports it.

OMAP3_CONTROL_OMAP_STATUS contains a bit we can use..

Based-on-patch-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: NeilBrown <neilb@suse.de>