Milk-V Duo and Duo-256M reserve a region for coprocessor FW at
the end of RAM. It is not correct because:
  - FSBL can be configured to load FW into a different region
  - if no firmware is loaded, the reserved memory is wasted

As explained in [1, 2], FSBL should reserve the region at runtime.

The latest FSBL can boot the system without coprocessor FW:
  FSBL Jb2829:g6f8962c394dd-dirty:2026-09-20T13:04:17+00:00
  st_on_reason=d0000
  st_off_reason=0
  P2S/0x1000/0xc00fa00.
  SD/0xaa00/0x1000/0x1000/0.P2E.
  cv181x DDR init.
  ddr_param[0]=0x0.
  pkg_type=5
  D1_3_2
  DDR3-2G-QFN
  Data rate=1866.
  DDR BIST PASS
  PLLS.
  PLLE.
  C2S/0x0/0x0/0x0.
  No C906L image.
  MS/0xba00/0x80000000/0x43e00.
  SD/0xba00/0x43e00/0x43e00/0.ME.
  L2/0x4f800.
  SD/0x4f800/0x200/0x200/0.L2/0x33334c42/0xcafe4b49/0x80200000/0x8c200/0x8c200
  SD/0x4f800/0x8c200/0x8c200/0.sys_switch_all_to_pll...
  Loader_2nd loaded.
  Use internal 32k

So it is safe to remove `coprocessor_rtos` nodes.

[1]: https://lore.kernel.org/sophgo/6e4b5c98-7d48-4629-a6a0-4d930327f9a0@sifive.com/
[2]: https://lore.kernel.org/sophgo/aqrhRic7Ww6fPhxg@pie/

Signed-off-by: Andrei Lalaev <andrey.lalaev@gmail.com>
---
Andrei Lalaev (2):
      riscv: dts: sophgo: cv1800b-milkv-duo: drop reserved memory node
      riscv: dts: sophgo: sg2002-milkv-duo256m: drop reserved memory node

 arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo.dts    | 11 -----------
 arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m.dts | 11 -----------
 2 files changed, 22 deletions(-)
---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20260921-sophgo-remove-coprocessor-node-4e6c59ab58d2

Best regards,
--  
Andrei Lalaev <andrey.lalaev@gmail.com>