ice: ice_aq_check_events: fix off-by-one check when filling buffer

Allow task's event buffer to be filled also in the case that it's size
is exactly the size of the message.

Fixes: d69ea414 ("ice: implement device flash update via devlink")
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>