lib/vdso: Remove VDSO_HAS_32BIT_FALLBACK

lib/vdso: Remove VDSO_HAS_32BIT_FALLBACK

VDSO_HAS_32BIT_FALLBACK was introduced to address a regression which
caused seccomp to deny access to the applications to clock_gettime64()
and clock_getres64() because they are not enabled in the existing
filters.

The purpose of VDSO_HAS_32BIT_FALLBACK was to simplify the conditional
implementation of __cvdso_clock_get*time32() variants.

Now that all the architectures that support the generic vDSO library
have been converted to support the 32 bit fallbacks the conditional
can be removed.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20190830135902.20861-5-vincenzo.frascino@arm.com
References: 9ca40fc01e97 ("lib/vdso/32: Provide legacy syscall fallbacks")