staging: omap-thermal: change Kconfig dependency method

Now arch code has to specify CONFIG_ARCH_HAS_BANDGAP. So, this driver
will be selectable only if the platform reports itself as having a
bandgap device.

Any OMAP variant or any other OMAP version needs to
	select ARCH_HAS_BANDGAP
so that the driver will be applicable. A part from that it is
required to device the data structures that maps the registers
and their bitfields. The DT compatible list must also be updated.

CC: Santosh Shilimkar <santosh.shilimkar@ti.com>
CC: Vaibhav Bedia <vaibhav.bedia@ti.com>

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