rtlwifi/rtl8188ee: Fix media status register mask

bt_msr & 0xfc will never match 0x3. Fix this by using a mask that actually matches the available types.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: John W. Linville <linville@tuxdriver.com>