powerpc/qspinlock: Rename yield_propagate_owner tunable

Rename yield_propagate_owner to yield_sleepy_owner, which better
describes what it does (what, not how).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Reviewed-by: "Nysal Jan K.A" <nysal@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231016124305.139923-7-npiggin@gmail.com