power: battery: Don't allow USB ICL callback to set CP ILIM for WLS

Whenever a change in USB ICL leads to setting the CP ILIM, check whether
DC is present first; don't set the CP ILIM if it is.

Change-Id: I8d6ca6b62c4d0475e332d67696c6167452e72139
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>