ARM: dts: msm: Disable VADC support for msmtitanium rumi

Few ADC channels are exposed under thermal sysfs. Thermal
engine will query ADC channels while booting. PMIC is not
emulated on RUMI, will result in kernel boot stuck issue.
Disable VADC support for msmtitanium rumi.

Change-Id: I95aafd238f4b526d97fb9ccc3f4688da33a8a3e9
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>