ixgbe: fix compilation with gcc-3.4

  CC [M]  drivers/net/ixgbe/ixgbe_main.o
drivers/net/ixgbe/ixgbe_main.c: In function `ixgbe_intr':
drivers/net/ixgbe/ixgbe_main.c:1290: sorry, unimplemented: inlining failed in call to 'ixgbe_irq_enable': function body not available
drivers/net/ixgbe/ixgbe_main.c:1312: sorry, unimplemented: called from here
make[4]: *** [drivers/net/ixgbe/ixgbe_main.o] Error 1

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>