MLK-9871 dts: imx6sx: remove canfd related stuff

The CANFD IP will be removed in final production, so remove
the CANFD related stuff in dts tree to avoid confusion.
The patch only removed user level in dts part, the exists related
clocks and pads in source code are still there which seems not matter.

Conflicts:

	arch/arm/boot/dts/Makefile
	arch/arm/boot/dts/imx6sx-sdb-canfd.dts
	arch/arm/boot/dts/imx6sx.dtsi

Signed-off-by: Dong Aisheng <b29396@freescale.com>
(cherry picked from commit d22d9374948d2461189a632263c2e18a13c9ea41)
(cherry picked from commit 9a0baefbd1030921e8755b9f6ebf36d19fdacfdf)