arm64: Hot-remove implementation for arm64

- arch_remove_memory interface
- kernel page tables cleanup
- vmemmap_free implementation for arm64

Change-Id: I8945b6b91ed7012abc1478de266302427ebeb639
Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
Signed-off-by: Maciej Bielski <m.bielski@virtualopensystems.com>
Patch-mainline: linux-kernel @ 11 Apr 2017, 18:25
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
Signed-off-by: Arun KS <arunks@codeaurora.org>
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
[swatsrid@codeaurora.org : Fix merge conflicts]
Signed-off-by: Swathi Sridhar <swatsrid@codeaurora.org>