dt-bindings: mtd: add sst25wf040b and en25s64 to sip-nor list

The chip sst25wf040b and en25s64 are compatible with SPI NOR flash.

Signed-off-by: Yuan Yao <yao.yuan@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>