ANDROID: sched: Don't allow frozen asymmetric tasks to remain on the rq

If a task with a restricted possible CPU mask and PF_FROZEN or
PF_FREEZER_SKIP set blocks, then we must not put it back on the runqueue
to handle a signal because this could lead to migration failures later
on if the suspending CPU is not capable of running it.

Return such a task to the runqueue only if a fatal signal is pending,
and otherwise allow the task to block.

Bug: 202918514
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I04cc9e65751f2bffc556c4da9ef02fe386764324