staging: r8188eu: fix memory leak in rtw_set_key

Before returning with an error we should free allocated buffers, since
they are not assigned to anywhere.

Fixes: 15865124 ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/ee783fbb71abb549505b84542223be7a7c905eea.1630692375.git.paskripkin@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>