MIPS: Alchemy: remove all CONFIG_SOC_AU1??? defines

Now that no driver any longer depends on the CONFIG_SOC_AU1???  symbols,
it's time to get rid of them: Move some of the platform devices to the
boards which can use them, Rename a few (unused) constants in the header,
Replace them with MIPS_ALCHEMY in the various Kconfig files.  Finally
delete them altogether from the Alchemy Kconfig file.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/2707/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index 4c34252..dbfa0f7 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -138,7 +138,7 @@
 
 config MTD_NAND_AU1550
 	tristate "Au1550/1200 NAND support"
-	depends on SOC_AU1200 || SOC_AU1550
+	depends on MIPS_ALCHEMY
 	help
 	  This enables the driver for the NAND flash controller on the
 	  AMD/Alchemy 1550 SOC.