Currently, this driver uses a 28bit interface to AHCI, this
limits the number of blocks addressable to 2^28, or the max
disk size to 512(2^28) or about 137GB. This change allows
supporting drives up to about 2TB.

Testing this is a bit difficult. There is test code that
can be inserted into U-Boot that will write test patterns
into certain unused blocks. These patterns can be manually
checked using 'dd' after boot. Another way is to confirm the
original error that exposed this bug is fixed. IOW: see if
AU (Auto Update) will now work on the drive. Also, check
that there are no warning messages from the 'cgpt' utility.

Signed-off-by: Walter Murphy <wmurphy@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>