For example,

  $ scripts/objdiff record init drivers/usb

disassembles all the objects under init and drivers/usb directories.

This feature would be useful when we change various files under the
specific directory.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: NJason Cooper <jason@lakedaemon.net>
Signed-off-by: NMichal Marek <mmarek@suse.cz>