UPSTREAM: arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0

Add a Kconfig entry to control use of the entry trampoline, which allows
us to unmap the kernel whilst running in userspace and improve the
robustness of KASLR.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 084eb77cd3a81134d02500977dc0ecc9277dc97d)

Change-Id: I70a996e448fa17007a3b8564c794e53e3992d7bf
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Git-commit: 16f712b4
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>