ARM: 7758/1: introduce config HAS_BANDGAP

Bandgap is a device used to measure temperature on electronic
equipments.  It is widely used in digital integrated circuits.  It is
based on the dependency between silicon voltage and temperature.

This patch introduce HAS_BANDGAP config entry.  This config is a boolean
value so that arch code can flag if they feature a bandgap device.

This config entry follows the same idea behind ARCH_HAS_CPUFREQ.

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-omap@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Fabio Stevam <festevam@gmail.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>