configs/mx6: Bump to kernel 4.8.11
Kernel 4.8.11 brings commit 5f95e68daae397 ("clk: imx: fix integer overflow
in AV PLL round rate"), which fixes a PLL calculation bug, so bump to this
version.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>