i.MX6: mx6q_sabrelite: add CONFIG_REVISION_TAG

i.MX6: mx6q_sabrelite: add CONFIG_REVISION_TAG

This is needed to support Freescale-supplied userspaces.

At the moment, both the IPU and VPU libraries provided by Freescale
in the "imx-lib" package contain routines which scrape the system
revision from /proc/cpuinfo. In the VPU library, this information is
used to load the proper firmware, allowing a single binary to be used
across various i.MX processors.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>