i2c: cadence: Handling Slave monitor mode

i2c: cadence: Handling Slave monitor mode

In slave monitor mode, the I2C interface is set up as a master and
continues to attempt a transfer to a particular slave until the
slave device responds with an ACK.

Added this feature for zero length transfers enable the controller
for slave monitor interrupt and get the status. Disable the slave
monitor mode feature upon successful handling.

Signed-off-by: Nava kishore Manne <navam@xilinx.com>
Acked-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>