ddb: don't limit pindex output in 'show vmopag'

[mhorne]

Summary

This command already prints a tremendous amount of output, and properly
obeys the pager. It does not make sense to arbitrarily limit the pages
that are printed, as the reader will not be aware that this has
happened.

[markj]

If I recall correctly, it wasn't always possible to interrupt the pager, so running certain ddb commands could make the debugger unusable and force a hard reset.