clk: clk_stm32f: No more need of 48Mhz from PLL_SAI

Initially, 48Mhz for SDIO clock was generated from SAI pll for
STM32F469 and STM32F746 SoCs, but this solution was not suitable
for STM32F429 SoCs.

A generic solution is to used the PLL_Q output as 48Mhz clock
for all STM32F SOCs family.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>