ipw2200 - Fix bad ipw_write8() macro

ipw_write8() can't be used alone with a loop because of a wrong definition.

  CC [M]  drivers/net/wireless/ipw2200.o
drivers/net/wireless/ipw2200.c: In function 'ipw_ethtool_set_eeprom':
drivers/net/wireless/ipw2200.c:10579: warning: array subscript is above array bounds
drivers/net/wireless/ipw2200.c: In function 'ipw_load':
drivers/net/wireless/ipw2200.c:2663: warning: array subscript is above array bounds

Add missing do {} while (0) to fix them.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>