x86/efi: Use all 64 bit of efi_memmap in setup_e820()

The efi_info structure stores low 32 bits of memory map
in efi_memmap and high 32 bits in efi_memmap_hi.

While constructing pointer in the setup_e820(), need
to take into account all 64 bit of the pointer.

It is because on 64bit machine the function
efi_get_memory_map() may return full 64bit pointer and before
the patch that pointer was truncated.

The issue is triggered on Parallles virtual machine and
fixed with this patch.

Signed-off-by: Dmitry Skorodumov <sdmitry@parallels.com>
Cc: Denis V. Lunev <den@openvz.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>