ARM: mm: cache-l2x0: Implement outer_clean_all()

There is already implemented full outer clean routine in
arch/arm/mm/cache-l2x0.c.

Make it possible to use it through outer_cache interface,
like other outer maintenance functions.

bug 983964

Change-Id: I47f1fad536c151c255e6a42d6517114c334ddfef
Reviewed-on: http://git-master/r/116074
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Kirill Artamonov <kartamonov@nvidia.com>
Tested-by: Kirill Artamonov <kartamonov@nvidia.com>
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-by: Justin Paver <jpaver@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>

Rebase-Id: Rf769958fea9fd10058a4805eeafe08f5f0e895dd

Conflicts:
	arch/arm/mm/cache-l2x0.c