{hw/i2c,docs/system/arm}: Allwinner TWI/I2C Emulation

{hw/i2c,docs/system/arm}: Allwinner TWI/I2C Emulation

This patch implements Allwinner TWI/I2C controller emulation. Only
master-mode functionality is implemented.

The SPL boot for Cubieboard expects AXP209 PMIC on TWI0/I2C0 bus, so this is
first part enabling the TWI/I2C bus operation.

Since both Allwinner A10 and H3 use the same module, it is added for
both boards.

Docs are also updated for Cubieboard and Orangepi-PC board to indicate
I2C availability.

Signed-off-by: Strahinja Jankovic <strahinja.p.jankovic@gmail.com>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20221226220303.14420-4-strahinja.p.jankovic@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>