dmaengine: dmatest: Allow negative timeout value to specify infinite wait

The dmatest module parameter 'timeout' is documented as accepting a -1 to mean
"infinite timeout". However, an infinite timeout is not advised, nor possible
since the module parameter is an unsigned int, which won't accept a negative
value. Change the parameter type to be signed integer.

Cc: Gary Hook <Gary.Hook@amd.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200424161147.16895-4-andriy.shevchenko@linux.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>