stm32mp1: add a core registers dump function

This function can be used to dump core registers
when an issue occurred. It will be automatically
called in debug mode and print information. It uses a first
core boolean to avoid unexpected dump information on a
SGI1 irq request also used for a standard core hotplug.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: I264bc6e4206e502a46e41c0820938032535a2058
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/186540


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>