ixgbe: fix data access on big endian cpu

1. cpu use data owned by ixgbe must use rte_le_to_cpu_xx(...)
2. cpu fill data to ixgbe must use rte_cpu_to_le_xx(...)
3. checking pci status with converted constant

Signed-off-by: Xuelin Shi <xuelin.shi@freescale.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>