net: ipa: list supported IPA versions in the Makefile

Create a variable in the Makefile listing the IPA versions supported
by the driver.  Use that to create the list of configuration data
object files used (rather than listing them all individually).

Add a SPDX license comment.

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