rtl8187: Fix lockups due to concurrent access to config routine

rtl8187: Fix lockups due to concurrent access to config routine

With the rtl8187 driver, the config routine is not protected against
access before a previous call has completed. When this happens, the
TX loopback that is needed to change channels may cause the chip to
be locked with a reset needed to restore communications. This patch
entered mainline as commit 7dcdd073bf78bb6958bbc12a1a47754a0f3c4721.

The problem was found by Herton Ronaldo Krzesinski <herton@mandriva.com.br>,
who also suggested this type of fix.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>