drivers: rmnet_perf: napi_gro_flush with flags

When we get a TCP or IP flag mismatch, don't
allow GRO to keep holding packets. Explicitly
flush it. This prevents the prevelance of OoO
packets.

Change-Id: Ifa6cb62d37a6a73b3864b75b60c759cb05ddfeca
Signed-off-by: Conner Huff <chuff@codeaurora.org>