msm: thermal: fix VDD restriction monitor not enabled case

KTM VDD restriction monitor is disabled if VDD apps node is not
defined or any issue in VDD apps device initialization. There are
some targets where VDD apps is not required, but vdd restriction
for other rails are still required.

Remove tight dependency on VDD apps for KTM VDD restriction monitor.

CRs-Fixed: 2064557
Change-Id: I0eea903ce782611b7d5d826732477e0bc07c57c2
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>