data xfer timeout

data transfer watchdog implemented. If data transfer will
take to long the data timeout interrupt will fire
and transfer will be aborted. Data xfer timeout is
configurable through wishbone interface.

additionaly, both timeout reg widths (cmd and data)
became configurable with defines.

Signed-off-by: Marek Czerski <ma.czerski@gmail.com>
block size reg change

this register must be set now to number of bytes in
single block minus 1 (value 0 means 1 byte long block)

Signed-off-by: Marek Czerski <ma.czerski@gmail.com>