devres: trivial whitespace fix

Everything else is indented with two spaces, so fix the odd one out.
Acked-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NPeter Rosin <peda@axentia.se>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/driver-model/devres.txt

@@ -335,7 +335,7 @@ MEM
   devm_kzalloc()
 
 MFD
- devm_mfd_add_devices()
+  devm_mfd_add_devices()
 
 PER-CPU MEM
   devm_alloc_percpu()