csky/vdso: Remove gettimeofday() and friends from VDSO

csky/vdso: Remove gettimeofday() and friends from VDSO

The time-related VDSO functionality was introduced in 2021 in
commit 87f3248cdb9a ("csky: Reconstruct VDSO framework") and
commit 0d3b051adbb7 ("csky: Add VDSO with GENERIC_GETTIMEOFDAY, GENERIC_TIME_VSYSCALL, HAVE_GENERIC_VDSO").

However the corresponding aux-vector entry AT_SYSINFO_EHDR was never
wired up, making these functions impossible to test or use.

The VDSO itself is kept as it also provides rt_sigreturn which is
exposed differently to userspace.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241010-vdso-generic-base-v1-1-b64f0842d512@linutronix.de