Add PCIe support by filling the COMPHY modes table.

Also add a new macro to generate the right value for the firmware
depending on the width (PCI x1, x2, x4, etc). The width will be passed
by the core as the "submode" argument of the ->set_mode() callback. If
this argument is zero, default to x1 mode.
Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
[miquel.raynal@bootlin.com: adapt the content to the mainline driver]
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>