sb800: move spi prefetch and fast read mode to sb bootblock.

sb800: move spi prefetch and fast read mode to sb bootblock.

So we don't waste time on the first cbfs scan.

Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
[adapt persimmon with the same change, and work around romcc bug
 in bootblock code: it doesn't like MEMACCESS[idx] |= value;]

Change-Id: Ic4d0e53d3102be0de0bd18b1b8b29c500bd6d997
Reviewed-on: http://review.coreboot.org/9
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Marc Jones <marcj303@gmail.com>