net: ipa: refer to IPA versions, not GSI

The GSI code is now exposed to IPA version numbers, and we handle
version-specific behavior based on the IPA version.

Modify some comments that talk about GSI versions so they reference
IPA versions instead.  Correct version number errors in a couple of
these comments.

The (comment) mapping between IPA and GSI versions in the definition
of the ipa_version enumerated type remains.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>