icnss: Avoid setting voltage for WCSSS_CX_MX

Due to changes in PMIC design, there is no need to set
absolute voltage for WCSS_CX_MX from APPS.
APPS will just enable regulator and voltage will be set
by WLAN PDC. Avoid setting voltage for WCSSS_CX_MX based
on min/max value from device tree.

Change-Id: I0bb9174eb1ebb791e6a8c760c05ed4bd870c6d46
Signed-off-by: Naman Padhiar <npadhiar@codeaurora.org>