dt-bindings: i2c: riic: Rename bindings documentation file

Rename the bindings documentation file for RIIC controller
from i2c-riic.txt to renesas,riic.txt.

This is part of an ongoing effort to name bindings documentation files for
Renesas IP blocks consistently, in line with the compat strings they
document.
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

MAINTAINERS

@@ -13658,7 +13658,7 @@ F:	drivers/i2c/busses/i2c-sh_mobile.c
 RENESAS RIIC DRIVER
 M:	Chris Brandt <chris.brandt@renesas.com>
 S:	Supported
-F:	Documentation/devicetree/bindings/i2c/i2c-riic.txt
+F:	Documentation/devicetree/bindings/i2c/renesas,riic.txt
 F:	drivers/i2c/busses/i2c-riic.c
 
 RENESAS USB PHY DRIVER