pinmux: stm32: l4: Make SPI SCK and MOSI pins Very High Speed

Ensure that the SPI SCK and MOSI pins are set to very high as slower
SPI speeds will cause device hangs when used. This is due to the state
changing too fast for hardware, causing RXE to never fire and thus
hang.

Signed-off-by: Pushpal Sidhu <psidhu.devel@gmail.com>