DPP: Fix bootstrapping URI parser to handle channel list for an opclass

DPP: Fix bootstrapping URI parser to handle channel list for an opclass

The bootstrapping URI format for DPP was extended during protocol design
to allow a list of channels without having to repeat the same operating
class information for each channel. That change was not included in the
initial implementation of the parser and a channel-list like
"C:81/1,6,11" would not be understood correctly (i.e., only the longer
"C:81/1,81/6,81/11" form would have been parsed correctly).

Fix this by extending the parser to accept both the shorter and longer
form for a list of channels within a single operating class.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>