usb: phy: qmp: Allow specifying regulator max load from DT

The PHY may have different load requirements depending on SoC
or platform. Allow for specifying the maximum load current
requirement for both core and vdda supplies from device tree
and use this value to pass to regulator_set_load(). Otherwise
use a default of 30mA.

Change-Id: Ia993e95e998f3d617a13843ba1829f9b39f4cf1a
Signed-off-by: Jack Pham <jackp@codeaurora.org>