Initial I2C implementation such that I2C sending and receiving now
works well enough to use the BMP280 driver for a BMP280 device connected
to any of I2C0-I2C6 on the default pins. I2CTOOL also works for these
interfaces.
Functionality for "no stop" and "no start" options is not present.
Implementing that is not clear from the peripheral datasheet and will be
a challenge.
Signed-off-by: Matteo Golin <matteo.golin@gmail.com>
903b6b168e