[U-Boot] i.MX6: mx6qsabrelite: allow use with Freescale 2.6.38 kernels

This series of patches is needed to allow main-line U-Boot to be used with Freescale's Linux 2.6.38 non-DT kernel releases.

These releases currently require at least the machine type and revision atag entries and are configured to load boot scripts from the ext3 filesystem.