With an Intel AHCI controller, the driver does not operate properly
if the requested amount of blocks to read exceeds 255.
It is probably possible to specify 0 as the block count and the driver
will read 256 blocks, but it was decided to limit the number of blocks
read at once to 128 (it should be a power of 2 for the optimal
performance of solid state drives).
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>