i2c: xiic: Add smbus_block_read functionality

smbus_block_read is added to xiic driver to read from few sensors
which support this command. Since the number of bytes to read is not
known prior to transfer, xiic standard mode is being used for low level
control of IP.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>