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

(cherry picked from commit ba31362694fe465b88a025ac7c35ad7f378efc86)
(cherry picked from commit f3a83b3a6257ea0fd5aba66ff42218350228b321)