ath9k_hw: remove AR9003 2.0 support

These chipsets will not hit the market, all customers will be
on >= AR9003 2.2. This shaves down the ath9k_hw size by
24161 bytes (24 KB) on my system.

Before:

$ size drivers/net/wireless/ath/ath9k/ath9k_hw.ko
   text	   data	    bss	    dec	    hex	filename
 292328	    616	   1824	 294768	  47f70	drivers/net/wireless/ath/ath9k/ath9k_hw.ko

$ du -b drivers/net/wireless/ath/ath9k/ath9k_hw.ko
5987825	drivers/net/wireless/ath/ath9k/ath9k_hw.ko

After:

$ size drivers/net/wireless/ath/ath9k/ath9k_hw.ko
   text	   data	    bss	    dec	    hex	filename
 277192	    616	   1824	 279632	  44450	drivers/net/wireless/ath/ath9k/ath9k_hw.ko

$ du -b drivers/net/wireless/ath/ath9k/ath9k_hw.ko
5963664	drivers/net/wireless/ath/ath9k/ath9k_hw.ko

Cc: Yixiang Li <yixiang.li@atheros.com>
Cc: Don Breslin <don.breslin@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>