arm64: dts: 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/3fee803a7464a3243e62a943a6a5dce8f1c65a2d.1624016811.git.geert+renesas@glider.be