LU-9679 osc: use assert_spin_locked()

LU-9679 osc: use assert_spin_locked()

assert_spin_locked() is preferred to spin_is_locked() for affirming
that a spinlock is locked.

__osc_extent_sanity_check() is only ever called with obj already
locked, so change the check into an assertion.

Linux-Commit: a12d8284b574 ("lustre: osc_cache: use
	assert_spin_locked()")

Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: Iaae6deb5af4dec4d31893749924f211ba0489c47
Reviewed-on: https://review.whamcloud.com/37596
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>