Add the TIF_PATCH_PENDING thread flag to enable the new livepatch
per-task consistency model for powerpc. The bit getting set indicates
the thread has a pending patch which needs to be applied when the thread
exits the kernel.
The bit is included in the _TIF_USER_WORK_MASK macro so that
do_notify_resume() and klp_update_patch_state() get called when the bit
is set.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>