staging: rtl8712: fix potential leak in r871x_wx_set_enc_ext()

staging: rtl8712: fix potential leak in r871x_wx_set_enc_ext()

Fix a potential leak in the error path of r871x_wx_set_enc_ext(). In case the
requested algorithm is not supported by the driver, the function returns
without freeing the already allocated 'param' struct. Move the input
verification to the beginning of the function so that the direct return is
safe. Detected by Coverity - CID 144373.

Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>