MFC r315572, r315573, r315575, r315578:

Add a module to build imx5 dtb files.

Add dtb/imx5 module build to the IMX53 kernel config.

Remove configs for IMX53-QSB and DIGI-CCWMX53. They were just
standard IMX53 with static dtb added, and now that imx53 can use vendor-
supplied dts files and ubldr, there is no need for a static-dtb variant.