kerneldump: remove physical argument from d_dumper

The physical address argument is essentially ignored by every dumper
method. In addition, the dump routines don't actually pass a real
address; every call to dump_append() passes a value of zero for
physical.

Reviewed by: markj
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D35173

(cherry picked from commit 489ba2223676ec251ab1bfe2906d2a62959c8ce3)