Add a shared NuttX I2C master lower-half for the Realtek Ameba I2C
controllers (I2C0/I2C1) in arch/arm/src/common/ameba, driven through
the SDK fwlib in polling mode. Per-chip wiring (controller count,
register bases, clock masks, crossbar pad-mux codes and the fwlib
I2C_InitTypeDef layout) lives in arch/arm/src/rtl8721dx/ameba_i2c_chip.h
so a port to the other Ameba chips only supplies a same-named header.
Each controller registers as /dev/i2cN from pke8721daf bring-up through
the stock I2C character driver; a dedicated `i2c` defconfig drives the
i2ctool for validation.
Assisted-by: Claude <noreply@anthropic.com>
Signed-off-by: dechao_gong <dechao_gong@realsil.com.cn>
dfc55c9bbe