enable read prefetching on O2micro bridges. It fixes the problems
seen with the RME Hammerfall DSP.
Thanks to Eric Still from O2micro for the input.

Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Daniel Ritz <daniel.ritz@gmx.ch>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>