stm32mp2: initial support

stm32mp2: initial support

Add initial support for STM32MP2 SoCs family.

SoCs information are available here :
https://www.st.com/content/st_com/en/campaigns/microprocessor-stm32mp2.html

Migrate all MP1 related code into stm32mp1/ directory
Create stm32mp2 directory dedicated for STM32MP2 SoCs.

Common code to MP1, MP13 and MP25 is kept into
arch/arm/mach-stm32/mach-stm32mp directory :
  - boot_params.c
  - bsec
  - cmd_stm32key
  - cmd_stm32prog
  - dram_init.c
  - syscon.c
  - ecdsa_romapi.c

For STM32MP2, it also :
  - adds memory region description needed for ARMv8 MMU.
  - enables early data cache before relocation.
    During the transition before/after relocation, the MMU, initially setup
    at the beginning of DDR, must be setup again at a correct address after
    relocation. This is done in enables_caches() by disabling cache, force
    arch.tlb_fillptr to NULL which will force the MMU to be setup again but
    with a new value for gd->arch.tlb_addr. gd->arch.tlb_addr has been
    updated after relocation in arm_reserve_mmu().

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>