rtl8187: don't set RTL818X_CONFIG3_GNT_SELECT flag on 8187B

The GNTSel bit should only concern pci devices by looking at RTL8180
spec, which is not the case of 8187B. Also testing shows that trying to
set this bit fails, a subsequent read from the register after trying to
set it shows that the bit isn't set, seems the hardware ignores it,
which makes sense. This setting was a left over from Realtek sources.

Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>