ACPI: introduce drivers/acpi/debugfs.c

Introduce drivers/acpi/debugfs.c.

Code for ACPI debugfs I/F,
i.e. /sys/kernel/debug/acpi/custom_method,
is moved to this file.

And make ACPI debugfs always built in,
even if CONFIG_ACPI_DEBUG is cleared.

BTW:this adds about 400bytes code to ACPI, when
CONFIG_ACPI_DEBUG is cleared.

[uaccess.h build fix from Andrew Morton <akpm@linux-foundation.org>]

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index f8f190e..0650e34 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -30,6 +30,12 @@
 static inline int acpi_debug_init(void) { return 0; }
 #endif
 
+#ifdef CONFIG_DEBUG_FS
+int acpi_debugfs_init(void);
+#else
+static inline int acpi_debugfs_init(void) { return 0; }
+#endif
+
 /* --------------------------------------------------------------------------
                                   Power Resource
    -------------------------------------------------------------------------- */