staging: wlags49_h2: Stop playing with length in GIWESSID handler

WE21 clarified that ESSID should not be NULL terminated.
The existing code didn't NULL terminate, but did play with length
and then reset it again. Just stop it.

Signed-off-by: David Kilroy <kilroyd@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>