Apply the same workaround for SDI flow control used on BCM5906 A1

Apply the same workaround for SDI flow control used on BCM5906 A1
to BCM6906 A0/A2. This should fix a long standing BCM5906 A2 lockup
issues. Data sheet explicitly mentions BCM5906 A0, A1 and A2 use
de-pipelined mode on these revisions.
Special thanks to Buganini who tried all combinations of
experimental patches for more than 10 days.

Tested by:	Buganini <buganini <> gmail dot com >