drivers/net/ixgbe: fix sparse warnings: make symbols static

Fix this sparse warnings:

  drivers/net/ixgbe/ixgbe_82598.c:180:5: warning: symbol 'ixgbe_get_copper_link_capabilities_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:245:5: warning: symbol 'ixgbe_setup_fc_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:729:5: warning: symbol 'ixgbe_set_vmdq_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:773:5: warning: symbol 'ixgbe_set_vfta_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:897:5: warning: symbol 'ixgbe_read_analog_reg8_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:919:5: warning: symbol 'ixgbe_write_analog_reg8_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:940:5: warning: symbol 'ixgbe_read_i2c_eeprom_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_82598.c:1000:5: warning: symbol 'ixgbe_get_supported_physical_layer_82598' was not declared. Should it be static?
  drivers/net/ixgbe/ixgbe_dcb_82598.c:100:5: warning: symbol 'ixgbe_dcb_config_packet_buffers_82598' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>