Remove -B from the DTSFILESCMD make dtb-y invocations

riscv: prevent "internal option" warning from make

Import Linux 6.10.3 DTS for RISC-V

This has the side effect of pulling in 5 arm64 renesas and a few other
dt-bindings files which didn't exist before so there are no conflicts.

Hopefully arm/arm64/mips can catch up soon.