net: ipa: restrict special reset to IPA v3.5.1

With IPA v3.5.1, if IPA aggregation is active at the time an
underlying GSI channel reset is performed, some special handling
is required.

There is logic in ipa_endpoint_reset() that arranges for that
special handling, but it's done for all hardware versions, not
just IPA v3.5.1.

Fix the logic to properly restrict the special behavior.

Signed-off-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20201102173435.5987-1-elder@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>