Bluetooth: Use correct endianness in L2CAP configuration fallback

Default RFC values should use le16 byte ordering. These values are
used only as a fallback when poorly-behaved remote devices do not send
a proper RFC option in an ERTM or streaming configuration response.

Change-Id: I51c9ae892f18229f568b354c92b64e3a8054b619
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>