ANDROID: GKI: reserve extra arm64 cpucaps for ABI preservation

Over the lifetime of the kernel, new arm64 cpucaps need to be added to
handle errata and other fun stuff.  So reserve 20 spots for us to use in
the future as this is an ABI-stable structure that we can not increase
over time without major problems.

Bug: 151154716
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I37bdac374e2570f61ab54919712fd62c7e541e67