net-test: enable CONFIG_GKI_NET_XFRM_HACKS

This is needed as part of deprecating CONFIG_ANDROID,
which is currently happening in android-mainline,
without this the 96 vs 128 bit xfrm portion of net test fails.

Bug: 252915518
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie34b2b4785a8debc687e2e6fce441885f5792fc0