arch/risc-v: Fix incompatible pointer types in vector context switching

[ENJOU1224]

Summary

The riscv_savevpu, riscv_restorevpu, and riscv_vpuregs functions were using uintptr_t * for vector registers, but tcb->xcp.vregs is defined as uintreg_t *. This mismatch caused compilation errors on newer GCC versions (e.g., GCC 13+) due to incompatible pointer types. This patch aligns the parameter types to uintreg_t * to match the structure definition.

Impact

Build: Fixes compilation warnings/errors on GCC 13+ toolchains regarding incompatible pointer types.
Hardware: RISC-V architectures with Vector extension enabled.
Compatibility: No functional change in runtime behavior (since uintptr_t and uintreg_t usually have the same width on RV32/RV64), but ensures source-level type safety.

Testing

Host Environment:

• OS: Ubuntu 25.10 (Linux 6.17.0-8-generic)
• Compiler: riscv64-unknown-elf-gcc (14.2.0+19) 14.2.0
• QEMU: QEMU emulator version 10.1.50 (v10.1.0-1314-gf3f2ad1193)

Verification Steps:

1. Compilation Fix verification:

   • Target: rv-virt:nsh (Modified to enable Vector extension)
   • Command: make -j
   • Before check: Build fails with error: passing argument 1 of 'riscv_savevpu' from incompatible pointer type on GCC 14.2.0.
   • After check: Build completes successfully without "incompatible pointer type" errors.

2. Runtime Verification:
   Booted the image on QEMU to ensure no regression in context switching initialization.

   Command:

   qemu-system-riscv32 \
         -nographic \
         -M virt \
         -bios none \
         -kernel ./nuttx \
         -cpu max,vlen=256,elen=64,v=true

   Boot Log:

   ABC
   NuttShell (NSH) NuttX-12.12.0
   nsh>