[patch, gprofng, riscv64] Fix build on Linux riscv64

[Sergey Fedorov]

The source unconditionally uses asm/hwprobe.h header, which is not
guaranteed to exit.
I was added recently in
https://github.com/torvalds/linux/commit/ea3de9ce8aa280c5175c835bd3e94a3a9b814b74

Add a check for Linux kernel version.
Tested on PinIx 2.1 riscv64, kernel 5.15.131.
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