drivers/pinmux: stm32: (FIX) Force very_high speed to SPIx_SCK gpio

Fix issue #9028: last bit of SPI/I2S transaction may be corrupted.
Impacted STM32 SOC series: F0/F1/F2/F3/F4/L0.

Notes:
- F2/F4/L0: set gpio to very_high speed ('11')
- F0/F3: set gpio to high speed ('11').
- F1: set gpio to 50MHz.

Signed-off-by: Armando Visconti <armando.visconti@st.com>