Use the module pointer to find the address we need to map to in the early
arm64 boot sequence. This will be a virtual address in the kernel space
after the kernel and any modules loaded by loader so we can use this to
find the size of the kernel + modules. We can then add on a level 2 page for
the module data and round up the size to be aligned to a level 2 page.

This allows more than 8 MiB of modules to be loaded by loader, e.g. zfs.ko
and opensolaris.ko.

Reported by: Shawn Webb
MFC after: 1 week
Sponsored by: DARPA, AFRL