src/arch: fix hwprobe include path and ZBC/ZVBC offsets for riscv64

src/arch: fix hwprobe include path and ZBC/ZVBC offsets for riscv64

Signed-off-by: WenLei <lei.wen2@zte.com.cn>
Fix runtime detection of RISC-V ZBC and ZVBC crypto extensions.

Problems fixed:
- <sys/hwprobe.h> only exists in glibc >= 2.40 (released 2024-07-22).
  Many production RISC-V distros still use older glibc (Ubuntu 22.04: 2.35,
  Debian 12: 2.36, etc.) and would fail to compile.
  Therefore we switch to the kernel UAPI header <asm/hwprobe.h>,
  which works with all current glibc versions.
  Proof:
  - Absent in glibc 2.39:
    https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h;hb=refs/tags/glibc-2.39
  - Present in glibc 2.40:
    https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h;hb=refs/tags/glibc-2.40
  - Introducing commit:
    https://sourceware.org/git/?p=glibc.git;a=commit;h=426d0e1aa8f17426d13707594111df712d2b8911

- Incorrect fallback bit positions:
  - RISCV_HWPROBE_EXT_ZBC was (1ULL << 15) → should be (1ULL << 7)
  - RISCV_HWPROBE_EXT_ZVBC was (1ULL << 20) → should be (1ULL << 18)

Signed-off-by: WenLei <lei.wen2@zte.com.cn>