Stub out the debugfs functions so that the build doesn't break when
CONFIG_DEBUG_FS=n.
Reported-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: NIan Munsie <imunsie@au1.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>