i2c: mlxcpld: Add support for smbus block read transaction

It adds support for smbus block read transaction. CPLD smbus block read bit
of capability register is verified during driver initialization, and driver
data is updated if such capability is available. In case an upper layer
requests a read transaction of length one and expects that length will be
the first received byte, driver will notify CPLD about SMBus block read
transaction flavor, so CPLD will know to execute such kind of transaction.

Signed-off-by: Michael Shych <michaelsh@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>