tree 5f35ba6c7e2f4eac0d63cbba1d20984e43aab7c4
parent 7c2fbbb61ca9bbfecea2278d0368c4e02038db3d
author Lei YU <mine260309@gmail.com> 1573034905 +0800
committer Lei YU <mine260309@gmail.com> 1575872081 +0800

i2c: Implement read function

Implement I2CDevice::read() by invoking i2c_smbus_read_xxx() APIs.
The code is referenced from i2c-tools' i2cget.c:

 https://github.com/ev3dev/i2c-tools/blob/ev3dev-stretch/tools/i2cget.c

Tested: Verify on Witherspoon that it reads the PSU ppgrade mode status
        register (1 byte) and CRC16 register (2 bytes) correctly.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I8759b6a35229f81120acf77f08429f7f79458b8b