ACPI: Improve acpi debug documentation

Now we use acpi.debug_level and acpi.debug_layer as kernel boot
parameters instead of acpi_dbg_level and acpi_dbg_layer.
Thanks to Andi Kleen for pointing it out.
Signed-off-by: NZhang Rui <rui.zhang@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

Documentation/kernel-parameters.txt

@@ -181,19 +181,41 @@ and is between 256 and 4096 characters. It is defined in the file
 			that require a timer override, but don't have
 			HPET
 
-	acpi_dbg_layer=	[HW,ACPI]
+	acpi.debug_layer=	[HW,ACPI]
 			Format: <int>
 			Each bit of the <int> indicates an ACPI debug layer,
 			1: enable, 0: disable. It is useful for boot time
 			debugging. After system has booted up, it can be set
-			via /proc/acpi/debug_layer.
-
-	acpi_dbg_level=	[HW,ACPI]
+			via /sys/module/acpi/parameters/debug_layer.
+			CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
+			Available bits (add the numbers together) to enable debug output
+			for specific parts of the ACPI subsystem:
+			0x01 utilities 0x02 hardware 0x04 events 0x08 tables
+			0x10 namespace 0x20 parser 0x40 dispatcher
+			0x80 executer 0x100 resources 0x200 acpica debugger
+			0x400 os services 0x800 acpica disassembler.
+			The number can be in decimal or prefixed with 0x in hex.
+			Warning: Many of these options can produce a lot of
+			output and make your system unusable. Be very careful.
+
+	acpi.debug_level=	[HW,ACPI]
 			Format: <int>
 			Each bit of the <int> indicates an ACPI debug level,
 			1: enable, 0: disable. It is useful for boot time
 			debugging. After system has booted up, it can be set
-			via /proc/acpi/debug_level.
+			via /sys/module/acpi/parameters/debug_level.
+			CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
+			Available bits (add the numbers together) to enable different
+			debug output levels of the ACPI subsystem:
+			0x01 error 0x02 warn 0x04 init 0x08 debug object
+			0x10 info 0x20 init names 0x40 parse 0x80 load
+			0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
+			0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
+			0x10000 resources 0x20000 user requests 0x40000 package.
+			The number can be in decimal or prefixed with 0x in hex.
+			Warning: Many of these options can produce a lot of
+			output and make your system unusable. Be very careful.
+
 
 	acpi_fake_ecdt	[HW,ACPI] Workaround failure due to BIOS lacking ECDT