ANDROID: arm64: add HWCAP2 flags to compat /proc/cpuinfo

Commit 72684eae ("arm64: Fix up
/proc/cpuinfo") backported the new /proc/cpuinfo handler to 3.10.69.
However since mainline 3.10 doesn't have the ARM HWCAP2 definitions,
this part was dropped from the backport.

android-3.10 *does* have these HWCAP2 definitions, so restore the
relevant parts from the original commit
(44b82b77).

Bug: 27982275

Change-Id: Ib62de783580e4c269c8e98c62ece9f8fc9e5836b
Signed-off-by: Greg Hackmann <ghackmann@google.com>