apparmor: Fix inverted comparison in cache_hold_inc()

apparmor: Fix inverted comparison in cache_hold_inc()

cache_hold_inc() prevents the per-CPU cache hold counter from
rising above MAX_HOLD_COUNT, but the comparison is inverted
(> MAX_HOLD_COUNT instead of <), so the counter never rises
above 0.

This breaks the cache mechanism because since the hold counter
is always 0, the global pool is always attempted first before
falling back to the local cache. The decrement also never occurs,
thus the hold counter is effectively dead.

Fix by changing > to < in cache_hold_inc().

Fixes: 0b6a6b72b329 ("apparmor: document the buffer hold, add an overflow guard")
Signed-off-by: Eduardo Vasconcelos <eduardo@eduardovasconcelos.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>