[PATCH 3/3] arm64: support flipped VA and 52-bit kernel VA

Linux 5.4 and later kernels for arm64 changed the kernel VA space
arrangement and introduced 52-bit kernel VAs by merging branch
commit b333b0ba2346.  Support 5.9+ kernels with vmcoreinfo entries
and 5.4+ kernels with best guessing.

However, the following conditions are not supported for now due to
no necessary information provided from kernel:
(1) 5.4 <= kernels <= 5.8 and
    - if PA_BITS=52 && VA_BITS!=52
    - with -x option if vabits_actual=52
(2) kernels < 5.4 with CONFIG_ARM64_USER_VA_BITS_52=y

(1) should be supported with kernel commit bbdbc11804ff and
1d50e5d0c5052 adding necessary information to vmcoreinfo.

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
Reviewed-by: Pingfan Liu <piliu@redhat.com>