media: rc: meson-ir: Add support for newer versions of the IR decoder

Newer SoCs (Meson 8b and GXBB) are using REG2 (offset 0x20) instead of
REG1 to configure the decoder mode. This makes it necessary to
introduce new bindings so the driver knows which register has to be
used.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>