staging: omap-thermal: introduze FREEZE_BIT feature

For ES2.0 devices, it is not guaranteed that current DTEMP
or DTEMP0 from the history buffer are going to contain
correct values, due to desynchronization between BG clk
and OCP clk.

For this reason, this patch changes the driver to first:
a. consider a feature flag, FREEZE_BIT, in order to check
it is possible to freeze the history buffer or not.
b. whenever reading the temperature, it will fetch from
DTEMP1 instead of DTEMP or DTEMP0.

This WA is applicable only for OMAP5430 ES2.0.

Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>