reset: stm32mp1_reset: add system reset management

Add the system reset management into the stm32mp
reset driver.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: I748f10de2398e1323160f479f99e92abd2f65dca
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/184412


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: Gabriel FERNANDEZ <gabriel.fernandez@st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>