VDSO_HAS_32BIT_FALLBACK has been removed from the core since
the architectures that support the generic vDSO library have
been converted to support the 32 bit fallbacks.

Remove unused VDSO_HAS_32BIT_FALLBACK from arm64 compat vdso.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20190830135902.20861-7-vincenzo.frascino@arm.com