ARM: dts: imx6dl-colibri-eval-v3: fix sram compatible properties

The sram-node compatible properties have mistakingly combined the
model-specific string with the generic "mtd-ram" string.

Note that neither "cy7c1019dv33-10zsxi, mtd-ram" or
"cy7c1019dv33-10zsxi" are used by any in-kernel driver and they are
not present in any binding.

The physmap driver will however bind to platform devices that specify
"mtd-ram".

Fixes: fc48e764 ("ARM: dts: imx6: Add support for Toradex Colibri iMX6 module")
Cc: Sanchayan Maity <maitysanchayan@gmail.com>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>