ARM: dts: imx6qdl-microsom: rename to imx6qdl-sr-som

Jon and myself feel that "imx6qdl-microsom" is too generic a name for
SolidRun's microsom - some other manufacturer could have their own
microsom.  Change the name to the shorter "imx6qdl-sr-som".

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>