lib/Kconfig: Do not select WW_MUTEX_SLOWPATH with PROVE_LOCKING

WW_MUTEX_SLOWPATH injects a deadlock defined with inject countdown which
have performace impacts.

Few frameworks like DRM has recovery mechanism when a deadlock is observed,
which releases all the locks and tries to re-aquire them causing delay in
displaying a frame onto the screen.

Change-Id: I60c647c33baf8bb35e9815400b06ad57e3a71dd7
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>