Revert "selftests: kselftest: Fix build failure with NOLIBC"

Revert "selftests: kselftest: Fix build failure with NOLIBC"

This reverts commit 16767502aa990cca2cb7d1372b31d328c4c85b40.

Nolibc gained support for uname(2) and sscanf(3) which are the
dependencies of ksft_min_kernel_version().

So re-enable support for ksft_min_kernel_version() under nolibc.

Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250209-nolibc-scanf-v2-2-c29dea32f1cd@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>