ARM: dts: OMAP5: Add bandgap DT entry

Add bandgap device DT entry for OMAP5 dtsi.

Cc: Tony Lindgren <tony@atomide.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: J Keerthy <j-keerthy@ti.com>
[benoit.cousson@linaro.org: Fix alignement and use the macros
for IRQ attributes]
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>