staging: ti-soc-thermal: Introduce HAS_HISTORY_BUFFER feature for bandgap

The patch introduces HISTORY_BUFFER feature. This is present in OMAP5 bandgap
and it is a hardware history buffer of previously read temperatures.

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