eal: add macro for attribute weak

eal: add macro for attribute weak

eal: add shorthand __rte_weak macro
qat: update code to use __rte_weak macro
avf: update code to use __rte_weak macro
fm10k: update code to use __rte_weak macro
i40e: update code to use __rte_weak macro
ixgbe: update code to use __rte_weak macro
mlx5: update code to use __rte_weak macro
virtio: update code to use __rte_weak macro
acl: update code to use __rte_weak macro
bpf: update code to use __rte_weak macro

Signed-off-by: Keith Wiles <keith.wiles@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>