platforms: fix KCU116 QSPI flash resources

Fix the dual QSPI flash resource shape so cs_n and dq are exposed as subsignals, correct the second flash chip select/data pins from UG1239, and add spiflash4x aliases for both devices.

Sources:

- https://docs.amd.com/r/en-US/ug1239-kcu116-eval-bd

- https://docs.amd.com/api/khub/documents/MyDbquCxOBksfDRrhBQM1A/content

Author: enjoy-digital

litex_boards/platforms/xilinx_kcu116.py

@@ -92,14 +92,23 @@
 
     # SPIFlash
     ("spiflash", 0, # clock needs to be accessed through primitive
-        Subsignal("cs_n"), Pins("AA12"),
-        Subsignal("dq"),   Pins("AD11 AC12 AC11 AE11"),
+        Subsignal("cs_n", Pins("AA12")),
+        Subsignal("dq",   Pins("AD11 AC12 AC11 AE11")),
+        IOStandard("LVCMOS18")
+    ),
+    ("spiflash4x", 0, # clock needs to be accessed through primitive
+        Subsignal("cs_n", Pins("AA12")),
+        Subsignal("dq",   Pins("AD11 AC12 AC11 AE11")),
         IOStandard("LVCMOS18")
     ),
-
     ("spiflash", 1, # clock needs to be accessed through primitive
-        Subsignal("cs_n"), Pins("U22"),
-        Subsignal("dq"),   Pins("N23 P23 R20 R21"),
+        Subsignal("cs_n", Pins("R20")),
+        Subsignal("dq",   Pins("N19 P23 N23 R21")),
+        IOStandard("LVCMOS18")
+    ),
+    ("spiflash4x", 1, # clock needs to be accessed through primitive
+        Subsignal("cs_n", Pins("R20")),
+        Subsignal("dq",   Pins("N19 P23 N23 R21")),
         IOStandard("LVCMOS18")
     ),