stm32mp1: correct IO compensation disabling

In stm32mp1_syscfg_disable_io_compensation(), to disable the IO
compensation cell, we have to set the corresponding bit in
SYSCFG_CMPENCLRR register, instead of clearing the bit in SETR register.

Change-Id: I510a50451f8afb9e98c24e1ea84efbf73a39e6b4
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/182085


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>