leds: qpnp-wled: Fix configuration of ovp register

The OVP register should not be configured based on the ovp-mv
device tree property if the disp-type-amoled property is
specified. Add a check to fix this.

CRs-Fixed: 1061297
Change-Id: Ibe42d1379af4f75377aec10eaa7bbaa1b4607605
Signed-off-by: Devesh Jhunjhunwala <deveshj@codeaurora.org>
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>