Staging: rtl8192u: Simplify error check code at prism2_wep_init

Simplify prism2_wep_init error check code employing goto when a failure is detected.
Removed pr_debug which was given a checkpatch.pl error because of literal string
 splitted across two lines of code, it was seldom going to be printed anyway.

Signed-off-by: Pedro Marzo Perez <marzo.pedro@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>