fpga: altera-cvp: Increase credit timeout

commit ec82dae4b4a85d369d313a9628873ade5095bcf7 from
https://github.com/altera-opensource/linux-socfpga.git



Increase the timeout for SDM (Secure device manager) data credits from
20ms to 40ms. Internal stress tests running at 500 loops failed with the
current timeout of 20ms. At the start of a FPGA configuration, the CVP
host driver reads the transmit credits from SDM. It then sends bitstream
FPGA data to SDM based on the total credits. Each credit allows the
CVP host driver to send 4kBytes of data. There are situations whereby,
the SDM did not respond in time during testing.

Signed-off-by: Ang Tien Sung <tien.sung.ang@intel.com>
Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>