[MIPS] Alchemy: move UART platform code to its proper place

Move the code registering the Alchemy UART platform devices from
drivers/serial/ to its proper place, into the Alchemy platform code.  Fix
the related Kconfig entry, while at it...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index f7cd950..34b809e 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -262,12 +262,12 @@
 	  cards.  If unsure, say N.
 
 config SERIAL_8250_AU1X00
-	bool "AU1X00 serial port support"
+	bool "Au1x00 serial port support"
 	depends on SERIAL_8250 != n && SOC_AU1X00
 	help
-	  If you have an Au1x00 board and want to use the serial port, say Y
-	  to this option.  The driver can handle 1 or 2 serial ports.
-	  If unsure, say N.
+	  If you have an Au1x00 SOC based board and want to use the serial port,
+	  say Y to this option. The driver can handle up to 4 serial ports,
+	  depending on the SOC. If unsure, say N.
 
 config SERIAL_8250_RM9K
 	bool "Support for MIPS RM9xxx integrated serial port"