r600/sb: give the scheduler more margin to find valid instructions groups

r600/sb: give the scheduler more margin to find valid instructions groups

For instruction sequences that change the address register with every load
the current limit to bail out of the scheduler and reject the optimisation
was too tight, i.e. it was expected that at least one pending instruction
would be scheduled each time.

Give the scheduler more margin to sort out these load sequences by allowing
a number of rounds where no instruction is scheduled.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106163

Signed-off-by: Gert Wollny <gw.fossdev@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>