iavf: remove "inline" functions from iavf_txrx.c

The iAVF txrx hotpath code has several functions that are marked as
"static inline" in the iavf_txrx.c file. This use of inline is frowned
upon in the netdev community and explicitly marked as something to avoid
in the Linux coding-style document (section 15).

Even though these functions are only used once, it is expected that GCC
is smart enough to decide when to perform function inlining where
appropriate without the "hint".

./scripts/bloat-o-meter is showing zero difference with this changes.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>