ANDROID: arch: arm64: vdso: export the symbols for time()

__cvdso_time() can be found in vDSO implementation,
but the symbols for time() are not exported.

Export the symbols and run bionic-benchmarks.

BEFORE:
bionic-benchmarks32 --bionic_extra BM_time_time
-----------------------------------------------------
Benchmark           Time             CPU   Iterations
-----------------------------------------------------
BM_time_time     83.6 ns         83.5 ns      8385964

bionic-benchmarks64 --bionic_extra BM_time_time
-----------------------------------------------------
Benchmark           Time             CPU   Iterations
-----------------------------------------------------
BM_time_time     63.5 ns         63.4 ns     11037509

AFTER:
bionic-benchmarks32 --bionic_extra BM_time_time
-----------------------------------------------------
Benchmark           Time             CPU   Iterations
-----------------------------------------------------
BM_time_time     8.57 ns         8.56 ns     81887312

bionic-benchmarks64 --bionic_extra BM_time_time
-----------------------------------------------------
Benchmark           Time             CPU   Iterations
-----------------------------------------------------
BM_time_time     7.52 ns         7.51 ns     93253809

Signed-off-by: Chiawei Wang <chiaweiwang@google.com>
Bug: 154668398
Bug: 157925983
Test: run bionic-benchmarks --bionic_xml vdso.xml
(cherry picked from fc30ad8ca60eccbce5245103fb4a2b070aa294de)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Change-Id: Ibd9835254c065801ba2f0976dffbf70d7bf0c85c