iio: adc: Kconfig: Make RZG2L_ADC depend on ARCH_RZG2L

ADC block is common on Renesas RZ/G2L and RZ/V2L SoC's, so instead of
adding dependency for each SoC's add dependency on ARCH_RZG2L. The
ARCH_RZG2L config option is already selected by ARCH_R9A07G044 and
ARCH_R9A07G054.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220406070315.13862-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>