Update this driver to support driver model. This involves implementing the
AHCI operations and reusing existing common code.

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

At present the AHCI uclass is just a shell and we still use the global
functions to access SATA. Fix this by adding operations to the uclass.

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

Driver model wants to use the core functions in this file but accesses the
uclass-private data in a different way. Move the code into new 'common'
functions and set up stubs to call these.

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

This function will not be used with driver model and it relates to the
other exported functions. Move it down next to them.

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

This variable is set but never used. Drop it.

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

Rename dwc_ahsata.h to indicate that it is a private header file. We plan
to create another header with some public functions.

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

Sort the header file inclusions into the correct order.

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

There is a strange &(var) coding style in this driver. Adjust it to use
&var instead, which is more usual.

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

With driver model sata_dev_desc[] does not exist. We still want to use the
common code of this driver so update it to pass struct ahci_uc_priv * to
each of these functions, instead of an integer which must be looked up in
sata_dev_desc[].

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

Most of the casts in this driver are not necessary. With driver model we
do not cast from void *. Update the driver to follow this rule.

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