stm32mp1: remove useless define

Remove STM32MP_DDR_SPEED_DFLT that is not used in STM32MP1 TF-A code.

Change-Id: I780cdc4e93a8a9d997d50f67cfc582acd4a353d6
Signed-off-by: Yann Gautier <yann.gautier@st.com>
1 file changed