ixgbe: combine accesses to FCTRL register into ixgbe_set_rx_mode

We are accessing the FCTRL register in multiple spots in the init path and
we can simplify things by combining the configuration all into
ixgbe_set_rx_mode.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>