ANDROID: GKI: prevent removal of monitored symbols

For aarch64 GKI builds, enable KMI_SYMBOL_LIST_ADD_ONLY also for
build_abi.sh, which is still supported on this branch.

One unused symbol got subsequently moved.

Fixes: 0152a475 ("ANDROID: add initial KMI representation and enable KMI enforcement")
Change-Id: I2d6bf2c23df971b230d3c2307d478d06dd182300
Signed-off-by: Matthias Maennich <maennich@google.com>