configs: freescale_imx*: bump to version 4.1.15_2.0.0_ga

This patch is based on the Yocto equivalent:
https://github.com/Freescale/meta-freescale/commit/f4e7a140
https://github.com/Freescale/meta-freescale/commit/d4c994cb
https://github.com/Freescale/meta-freescale/commit/7ad6dcc3



Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Cc: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>