configs: stm32fxxx: Remove CONFIG_SYS_CLK_FREQ

Since commit aa5e3e22f4d6 ("board: stm32: switch to DM STM32 timer")
SYS_CLK_FREQ is useless, remove it from stm32f4 and stm32f7 boards.

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