wic: Update the help text to include -D (--debug)

wic: Update the help text to include -D (--debug)

The --debug option is missing from the wic help text; this adds it and
at the same time rearranges the usage into a more logical arrangement.

(From OE-Core rev: cf5144ef241d8f4ccaa3461ae5c9f89c2cf2f8d1)

(From OE-Core rev: e7f18c43f1b368b71acdc507e1a9035179d7e53f)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>