Use cached context version if available
Use cached context version if available

If the backend initialized the private iio_context fields .major, .minor
and .git_tag, use them instead of issuing a call to the backend's
.get_version() callback.

Signed-off-by: Paul Cercueil <a027184a55211cd23e3f3094f1fdc728df5e0500@crapouillou.net>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio