Documentation: Replace obsolete "driverfs" with "sysfs".

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

diff --git a/Documentation/pnp.txt b/Documentation/pnp.txt
index 481faf5..a327db6 100644
--- a/Documentation/pnp.txt
+++ b/Documentation/pnp.txt
@@ -17,9 +17,9 @@
 ------------------
 	The Linux Plug and Play user interface provides a means to activate PnP devices
 for legacy and user level drivers that do not support Linux Plug and Play.  The 
-user interface is integrated into driverfs.
+user interface is integrated into sysfs.
 
-In addition to the standard driverfs file the following are created in each 
+In addition to the standard sysfs file the following are created in each
 device's directory:
 id - displays a list of support EISA IDs
 options - displays possible resource configurations