Correct gcc warning of using too much stack debugfs_read.  This is done
by kmallocing the buffer instead of using the char array on stack.
Also, shrinking the buffer to something closer to what is currently
being used.
Signed-off-by: NJon Mason <jon.mason@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>