ixgbe: Make sure boolean assignments from bitwise operations done correctly

When the link comes up, the driver detects which flow control settings are
active.  This is done using bitwise operations directly from the hardware
registers, and assumes the proper boolean assignment.  Make this an
explicit boolean value before assignment to the bool.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>