Revert "ANDROID: arm64: temporarily mark ARM64_SW_TTBR0_PAN as BROKEN"

The previous patch fixed the breakage caused by moving thread_info
around, so we can re-enable this option.

This reverts commit 223afa4d71f73309ba78da33ed0f362229ecb368.

Change-Id: I4f43b05938055ebe791a8d128f6b8b0aa5bb2d27
Signed-off-by: Greg Hackmann <ghackmann@google.com>