[PATCH] net/iavf: fix old GCC compilation warnings

[Stephen Hemminger]

On Fri,  9 Jun 2023 13:41:56 +0800
Zhichao Zeng <zhichaox.zeng at intel.com> wrote:

> The code uses the Wimplicit-fallthrough compile option to ignore
> falls through warnings in switch case, but this option was introduced
> by GCC 7 and old GCC do not recognize the option.
> 
> Add judgment to avoid warnings about unrecognized options in old GCC.
> 
> Fixes: 95a1b0b23140 ("net/iavf: support Rx timestamp offload on SSE")
> Fixes: 4f58266da4d3 ("net/iavf: support Rx timestamp offload on AVX2")
> Fixes: d65eadb9e178 ("net/iavf: support Rx timestamp offload on AVX512")
> Signed-off-by: Zhichao Zeng <zhichaox.zeng at intel.com>
> ---

RHEL 7 becomes end of life this month.
That makes the oldest version of Gcc that DPDK is required to support
is gcc 8.X in RHEL 8.