Allow impls to ignore incremental scan interval

When incremental results are disabled for network scans,
update the API documentation to allow implementations to
ignore range checking for the incremental scan interval.

Bug: 112486807
Test: compilation - docstring-only change
Merged-In: I901335550b4b8c2cf75f91b39fd031f03ffae982
Change-Id: I901335550b4b8c2cf75f91b39fd031f03ffae982
(cherry picked from commit 944efca7)