ipw2x00: remove ipw2100_rates_11b[]

It's just a duplicate of ipw2100_bg_rates[].

Signed-off-by: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Reviewed-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>