dmaengine: dmatest: add norandom option

Existing option noverify disables both random src/dst address offset
setup and data verification. Sometimes, we need to control random
src/dst address setup and verification separately, such as disabling
random to make sure that test covers addresses in all interleaving
banks, but data verification is still performed.

This patch adds option norandom to disable random offset setup. Option
noverify has been changed to disable data verification only.

Cc: Joey Zheng <yu.zheng@hxt-semitech.com>
Signed-off-by: Yang Shunyong <shunyong.yang@hxt-semitech.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>