drivers: thermal: Add support to modify passive/polling delay to of_thermal

Whenever userspace modifies thermal zone passive delay or polling
delay from sysfs, of_thermal can reset this value to devicetree
defaults while re-enabling thermal zone. Add support to update
passive delay and polling delay to the of_thermal framework so that
userspace can modify and retain the delay across multiple disable
and enable actions.

Change-Id: I68c2bcd2eebeeffa48b3f8ecfb2882c77ff9d6ee
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>