ixgbe: remove unused function prototypes

DPDK commit message

net/ixgbe/base: remove unused function prototypes
There are some function prototypes that were introduced at some point
but were never implemented, so remove them.

Signed-off-by: Chinh Cao <chinh.t.cao@intel.com>

Obtained from: DPDK (e9cc1b4)

(cherry picked from commit 420c984470270e0f7200124d8015236584aef243)