clk: renesas: rzg2: Rename i2c-dvfs to iic-pmic

As RZ/G2 SoCs do not support DVFS, the "iic-dvfs" module was renamed to
"iic-pmic" in the RZ/G Series, 2nd Generation User’s Manual: Hardware
Rev. 1.00.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/3e549b41989ff2797b998a1c749c9f607845f44a.1624016693.git.geert+renesas@glider.be