dts: arm: st: h7: correct stm32h723 memory regions

* Corrects SRAM0 size. The `TCM_AXI_SHARED`
  is `000` after reset. That means ITCM
  is shared with SRAM0.
* Adds missing SRAM1,2,4, and ITCM
  regions.
* Adds label and compatible properties
  to the flash section.

Signed-off-by: Georgij Cernysiov <geo.cgv@gmail.com>