ARM: shmobile: r8a7740 dtsi: Correct IIC0 parent clock

According to the datasheet, the operating clock for IIC0 is the HPP
(RT Peri) clock, not the SUB (Peri) clock. Both clocks run at the same
speed (50 Mhz).

This is consistent with IIC0 being located in the A4R PM domain, and
IIC1 in the A3SP PM domain.

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