vdso: Add prototype for __vdso_clock_getres_time64()

vdso: Add prototype for __vdso_clock_getres_time64()

For consistency with __vdso_clock_gettime64() there should also be a
64-bit variant of clock_getres(). This will allow the extension of
CONFIG_COMPAT_32BIT_TIME to the vDSO and finally the removal of 32-bit
time types from the kernel and UAPI. The generic vDSO library already
provides nearly all necessary building blocks for architectures to
provide this function. Only a prototype is missing.

Add the prototype to the generic header so architectures can start
providing this function.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20251223-vdso-compat-time32-v1-1-97ea7a06a543@linutronix.de