defconfig: ginkgo: turn on VDSO

Turn on the vdso32 feature on an arm64 kernel.

Results in roughly a 4 fold speedup for clock_gettime() and other
timekeeping functions for arm32 executables in the environment.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 20045882
Bug: 19198045
Bug: 63737556
Change-Id: If39bfad8b287a5455dc8240a73dcc8951e4bc13f