dt-bindings: clk: r7s72100: Add missing I and G clocks

Add the missing definitions for the I (CPU) and G (Image Processing)
clocks, so these clocks can be referred to from device nodes in DT.

Note that these clocks are already fully supported otherwise (DT
bindings, Linux driver, r7s72100.dtsi), they were just omitted from the
header file.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>