disp: msm: add connector API to disable cont_splash resource votes

The panel regulator votes are added by default during
dsi probe to make sure sync state driver doesn't disable
these regulators for cont_splash use case. These regulator
votes need to be removed when cont_splash feature is
disabled. Add a new connector API to handle this.

CRs-Fixed: 2734419
Change-Id: Ie54c8f246877a042afacddaeae8b90440652116f
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>