Revert "dt-bindings: i2c: rcar: Rename bindings documentation file"

This reverts commit d13ed84b.
I overlooked that the Rev-by tag was given in advance assuming a fix was
made for the next revision.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

MAINTAINERS

@@ -13650,7 +13650,7 @@ F:	drivers/iio/adc/rcar-gyroadc.c
 RENESAS R-CAR I2C DRIVERS
 M:	Wolfram Sang <wsa+renesas@sang-engineering.com>
 S:	Supported
-F:	Documentation/devicetree/bindings/i2c/renesas,i2c.txt
+F:	Documentation/devicetree/bindings/i2c/i2c-rcar.txt
 F:	Documentation/devicetree/bindings/i2c/renesas,iic.txt
 F:	drivers/i2c/busses/i2c-rcar.c
 F:	drivers/i2c/busses/i2c-sh_mobile.c