IB/usnic: Change WARN_ON to lockdep_assert_held

IB/usnic: Change WARN_ON to lockdep_assert_held

usNIC calls WARN_ON(spin_is_locked..) at few places.  In some of these
instances, the call is made while holding a spinlock.  Change
all WARN_ON(spin_is_locked...) calls in usNIC to
lockdep_assert_held to make it fool-proof bc the latter can be
called while holding a spinlock and unlike spin_is_locked,
lockdep_assert_held also works correctly on UP.

Signed-off-by: Upinder Malhi <umalhi@cisco.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>