i2c: Add Tegra BPMP I2C proxy driver

Add Tegra BPMP I2C driver. The BPMP is the boot and power management
processor embedded in Tegra SoCs. In newer SoC versions, access to one
of the I2C busses goes via the BPMP, requiring a different "proxy" I2C
driver that accesses the bus via the real I2C driver embedded in the
BPMP firmware.

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>