MIPS: Loongson: Remove the serial port output of compressed kernel support

The compressed kernel support on loongson family machines is stable now,
so, remove the debug information via using SYS_SUPPORTS_ZBOOT instead of
SYS_SUPPORTS_ZBOOT_UART16550. This may reduce the image size and speedup
the booting.
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: yanh@lemote.com
Cc: huhb@lemote.com
Cc: zhangfx@lemote.com
Patchwork: http://patchwork.linux-mips.org/patch/824/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -180,7 +180,7 @@ config LASAT
 
 config MACH_LOONGSON
 	bool "Loongson family of machines"
-	select SYS_SUPPORTS_ZBOOT_UART16550
+	select SYS_SUPPORTS_ZBOOT
 	help
 	  This enables the support of Loongson family of machines.