Revert "selftests: vDSO: parse_vdso: Use UAPI headers instead of libc headers"

Revert "selftests: vDSO: parse_vdso: Use UAPI headers instead of libc headers"

This reverts commit c9fbaa879508 ("selftests: vDSO: parse_vdso: Use UAPI
headers instead of libc headers")

The kernel headers were used to make parse_vdso.c compatible with
nolibc.  Unfortunately linux/elf.h is incompatible with glibc's
sys/auxv.h. When using glibc it is therefore not possible build
parse_vdso.c as part of the same compilation unit as its caller
as sys/auxv.h is needed for getauxval().

In the meantime nolibc gained its own elf.h, providing compatibility
with the documented libc interfaces.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260227-vdso-selftest-cleanups-v2-1-d84830fa8beb@linutronix.de