sprandom: add command line options

Add sprandom command line options:
1. boolean sprandom:  enables the sprandom flow.
2. spr_num_regions: granularity of sprandom, defaults to 100
3. spr_op: over provisioning factor, defaults to 0.15

Signed-off-by: Tomas Winkler <tomas.winkler@sandisk.com>
6 files changed