read transfers

Added standard mode for AXI I2C controller to enable read transfers
of size more than 255 bytes. The driver selects standard mode in the
following scenarios.

1. If a single message request comes from user space, requesting a
read of more than 255 bytes

2. If a message set request comes from user space consisting of many
messages and if any one of them is a read operation, irrespective
of the size of transfer. (This is done because it is observed that
repeated start operation is not happening in dynamic mode read as
expected in a message set request from user space.)
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>