This patch adds support for a new backoff algorithm for half duplex 
supported in newer hardware. The old method is will be designated as 
legacy mode.

Re-seeding random values for the backoff algorithms are performed when a 
transmit has failed due to a maximum retry count (1 to 15, where max is 
considered the wraparound case of 0).

** Resending based on further feedback: Removed unnecessary miniseeds, 
fixed up combined seed usage, fixed size of global seed sets.

Signed-off-by: Ayaz Abdulla <aabdulla@nvidia.com>