riscv: dts: Add initial Anlogic DR1V90 SoC device tree

riscv: dts: Add initial Anlogic DR1V90 SoC device tree

DR1V90 is a FPSoC from Anlogic, which features a RISC-V core as the PS
part and 94,464 LUTs for the PL part.

The PS part integrates a Nuclei UX900 RISC-V core with 32KB L1 icache
and 32KB L1 dcache. It also provides two "snps,dw-apb-uart" compatible
UART controllers.

Some basic information of the processor can be obtained by running a
simple application from nuclei-sdk [1]:

-----Nuclei RISC-V CPU Configuration Information-----
         MARCHID: 0xc900
          MIMPID: 0x20300
             ISA: RV64 A B C D F I M P S U
            MCFG: TEE ECC ECLIC PLIC PPI ILM DLM ICACHE DCACHE IREGION No-Safety-Mechanism DLEN=VLEN/2
             ILM: 256 KB has-ecc
             DLM: 256 KB has-ecc
          ICACHE: 32 KB(set=256,way=2,lsize=64,ecc=1)
          DCACHE: 32 KB(set=256,way=2,lsize=64,ecc=1)
             TLB: MainTLB(set=32,way=2,entry=1,ecc=1) ITLB(entry=8) DTLB(entry=8)
         IREGION: 0x68000000 128 MB
                  Unit        Size        Address
                  INFO        64KB        0x68000000
                  DEBUG       64KB        0x68010000
                  ECLIC       64KB        0x68020000
                  TIMER       64KB        0x68030000
                  PLIC        64MB        0x6c000000
     INFO-Detail:
                  mpasize : 0
             PPI: 0xf8000000 128 MB
-----End of Nuclei CPU INFO-----

Link: https://github.com/Nuclei-Software/nuclei-sdk/blob/master/application/baremetal/cpuinfo/main.c
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>