rtl8xxxu: fix typo on variable name, compare against correct variable

path_b_ok is being assigned but immediately after path_a_ok is being
compared to the value 0x03.  This appears to be a typo on the
variable name, compare path_b_ok instead.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>