RISC-V: hwprobe: Always use u64 for extension bits

RISC-V: hwprobe: Always use u64 for extension bits

Extensions are getting added quickly and their hwprobe bits will soon
exceed 31 (which pair values accommodate, since they're of type u64).
However, in one tree, where a bunch of extensions got merged prior to
zicboz, zicboz already got pushed to bit 32. Pushing it exposed a
32-bit compilation bug, since unsigned long was used instead of u64.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310311801.hxduISrr-lkp@intel.com/
Fixes: 9c7646d5ffd2 ("RISC-V: hwprobe: Expose Zicboz extension and its block size")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20231101141908.192198-2-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>