arm64: Make kern_delta unneeded in the boot params

Use pmap_early_vtophys to translate from a virtual to physical where
we were previously using the calculated delta. This means that, while
we still calculate it, we don't need to pass it to initarm or either
pmap bootstrap functions.

While here remove an unneeded printf that indirectly used it or was
related to the previous printf.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D42567