staging: rtl8192u: fix incorrect mask and shift on u8 data

The cfg_action bit comes from the high bit of pmsg[4] so the
current mask and shift are in correct and always result in
zero.  Fix this by using the correct mask and shif to get the
correct cfg_action bit value.

Detected by CoverityScan, CID#142890 ("Operands don't affect result")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>