Remove skip_permanent_breakpoint gdbarch hook
The skip_permanent_breakpoint gdbarch hook has been obsolete since:
commit 61a12cfa7b25746914493cc0d94e5053a8492aa5
Author: Jan Kratochvil <jan.kratochvil@redhat.com>
Date: Fri Mar 13 20:24:22 2015 +0100
Remove HPUX
This patch removes it.