power: supply: cpcap-charger: Enable vbus boost voltage

We are currently not enabling VBUS boost for cpcap when in host mode.
This means the VBUS is fed at the battery voltage level, which can cause
flakeyness enumerating devices.

Looks like the boost control for VBUS is CPCAP_BIT_VBUS_SWITCH that we
must enable in the charger for nice 4.92 V VBUS output. And looks like
we must not use the STBY pin enabling but must instead use manual VBUS
control in phy-cpcap-usb.

We want to do this in cpcap_charger_vbus_work() and also set a flag for
feeding_vbus to avoid races between USB detection and charger detection,
and disable charging if feeding_vbus is set.

Cc: Jacopo Mondi <jacopo@jmondi.org>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Marcel Partap <mpartap@gmx.net>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Michael Scott <hashcode0f@gmail.com>
Cc: NeKit <nekit1000@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>