dt-bindings: crypto: fsl: add clock for caam snvs

Add "clock" property (and corresponding "clock-names")
for the CAAM SNVS node.

This property is optional: there are cases when SNVS clock is kept
always on (chips such as i.MX6 SX, UL).
A good guide line is to check whether i.MX clk driver defines the clock.

Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>

Documentation/devicetree/bindings/crypto/fsl-sec4.txt

@@ -387,7 +387,7 @@ EXAMPLE
 
 =====================================================================
 CAAM SNVS Node
-  Load the SECVIO node.
+  Load the CAAM SNVS node.
 
   - compatible
       Usage: required
@@ -401,6 +401,18 @@ CAAM SNVS Node
           address and length of the SEC4 configuration
           registers.
 
+   - clocks
+      Usage: required if i.MX clk driver defines an SNVS clock
+      Value type: <prop_encoded-array>
+      Definition:  Phandle and clock specifier pair describing
+          the clock required for enabling and disabling SNVS.
+
+   - clock-names
+      Usage: required if i.MX clk driver defines an SNVS clock
+      Value type: <string>
+      Definition: Clock name string corresponding to the clock
+          in the clocks property.
+
 =====================================================================
 Security Violation (SECVIO) Node
   Reports security violations.