soc: stm32f4: add pinmux defs for usb on pb14 and pb15
soc: stm32f4: add pinmux defs for usb on pb14 and pb15

USB High Speed port on STM32F4 SoCs is pinned out from the
pin PB14 and PB15.

Signed-off-by: Jun Li <3d873abd46e48a508cfeae575fcd9ffe09e1a769@intel.com>

kraj/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,kraj/zephyr,explora26/zephyr,kraj/zephyr,finikorg/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,explora26/zephyr,galak/zephyr,Vudentz/zephyr,explora26/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,galak/zephyr,ldts/zephyr,nashif/zephyr,finikorg/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,ldts/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,punitvara/zephyr,kraj/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr