powerpc: Consolidate {k,u}probe definitions

Move is_trap() and relatives to a common file to be shared between kprobes
and uprobes.

Code movement only; no change in functionality.

Suggested by Michael Ellerman.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>