dt: bindings: move SEC node under new crypto/

Since technically it's not powerpc arch-specific.  Also rename it sec2
to differentiate it from its incompatible successor, the SEC 4.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

Documentation/devicetree/bindings/crypto/fsl-sec2.txt

@@ -1,4 +1,4 @@
-Freescale SoC SEC Security Engines
+Freescale SoC SEC Security Engines versions 2.x-3.x
 
 Required properties: