stpmic: add usb otg regulators

Add regulators boost, pwr_sw1 and pwr_sw2 regulators related to
USB OTG supply BOOST, SW_OTG and SWIN/SWOUT. These regulators are
needed since manipulated during the suspend/resume power sequence
as per FDT description for stm32mp15x-xxx boards from
STMicroelectronics.

Change-Id: I6217de707e49882bd5a9100db43e0d354908800d
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/155145


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>
Reviewed-by: CIBUILD <smet-aci-builds@lists.codex.cro.st.com>