vc/amd/fsp/picasso: add comment on logical lane numbers in descriptor

The expected lane numbers in the fsp_pcie_descriptor struct are the
logical and not the physical ones.

Change-Id: I14166bbd397a9e5f5c5370717e039b9e71cbdb07
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43311
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/vendorcode/amd/fsp/picasso/platform_descriptors.h

@@ -110,6 +110,7 @@ typedef struct __packed {
 } fsp_ddi_descriptor;
 
 /* Picasso PCIe Descriptor: used for assigning lanes, bifurcation and other settings */
+/* Beware that the lane numbers in here are the logical and not the physical lane numbers! */
 typedef struct __packed {
 	uint8_t		engine_type;
 	uint8_t		start_lane;			// Start lane of the pci device