rtl8187: Change detection of RTL8187B with USB ID of 8187

Some early versions of RTL8187B devices have a USB ID of 0x8187
rather than the 0x8189 of later models. In addition, it appears
that these early units also must be programmed with lower power.
Previous patches used the Product ID string to detect this situation,
but did not address the low power question. This patch uses the
hardware version and sets the power accordingly.

Signed-off-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>