i40e: Fix bit logic error in failure case

Patch a036244c "i40e: Fix kernel panic on enable/disable LLDP"
introduced an error in bit logic.

Originally this bit manipulation was meant to clear two bits to indicate
that DCB was not enabled or capable. An "&" was incorrectly used instead
of an "|" bit operator to combine the two bitmasks into one.  This also
created a static checker error since the resultant code was a no-op.

This patch fixes the error by using the correct bit-wise operator.

Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>