fdts: stm32mp1: update stpmic1 configuration

Align STPMIC1 configuration with linux.

Signed-off-by: Pascal Paillet <p.paillet@st.com>
Change-Id: I4efaa889fec4337ab2516daf17452f63f874a757
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/144883


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: CIBUILD <smet-aci-builds@lists.codex.cro.st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>