genksyms: adjust the output format to modpost

genksyms: adjust the output format to modpost

Make genksyms output symbol versions in the format modpost expects,
so the 'sed' is unneeded.

This commit makes *.symversions completely unneeded.

I will keep *.symversions in .gitignore and 'make clean' for a while.
Otherwise, 'git status' might be surprising.

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Nicolas Schier <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Tested-by: Sedat Dilek <[email protected]> # LLVM-14 (x86-64)