Use the module pointer to find the address we need to map to in the early

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