arm: rmobile: Support RZ/G2L memory map

The memory map for the RZ/G2L family differs from that of previous R-Car
Gen3/Gen4 SoCs.

A high level memory map can be seen in figure 5.2 (section 5.2.1) of the
RZ/G2L data sheet rev 1.30 published May 12, 2023. A summary is included
here (note that this is a 34-bit address space):
  * 0x0_0000_0000 - 0x0_0002_FFFF SRAM area
  * 0x0_0003_0000 - 0x0_0FFF_FFFF Reserved area
  * 0x0_1000_0000 - 0x0_1FFF_FFFF I/O register area
  * 0x0_2000_0000 - 0x0_2FFF_FFFF SPI Multi area
  * 0x0_3000_0000 - 0x0_3FFF_FFFF Reserved area
  * 0x0_4000_0000 - 0x1_3FFF_FFFF DDR area (4 GiB)
  * 0x1_4000_0000 - 0x3_FFFF_FFFF Reserved area

Within the DDR area, the first 128 MiB are reserved by TrustedFirmware.
The region from 0x43F00000 to 0x47DFFFFF inclusive is protected for use
in TrustedFirmware/OP-TEE, but all other memory is included in the
memory map. This reservation is the same as used in R-Car
Gen3/Gen4 and RZ/G2{H,M,N,E} SoCs.

DRAM information is initialised based on the data in the fdt.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>