dt/bindings: exynos-rng: Move dt binding documentation to bindings/crypto

Samsung exynos PRNG driver is using crypto framework instead of
hw_random framework. So move the devicetree binding to crypto folder.

Signed-off-by: PrasannaKumar Muralidharan <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

MAINTAINERS

···
 L:	[e-mail]
 S:	Maintained
 F:	drivers/crypto/exynos-rng.c
-F:	Documentation/devicetree/bindings/rng/samsung,exynos-rng4.txt
+F:	Documentation/devicetree/bindings/crypto/samsung,exynos-rng4.txt
 
 SAMSUNG FRAMEBUFFER DRIVER
 M:	Jingoo Han <[e-mail]>