If we are in NETWORK SLEEP state, AR_SLP32_TSF_WRITE_STATUS limit
always exceeds in 'ath9k_hw_reset_tsf', because reading of the
AR_SLP3 register always return with the magic 0xdeadbeef value.
Changes-licensed-under: ISC Signed-off-by: Gabor Juhos <juhosg@openwrt.org> Signed-off-by: John W. Linville <linville@tuxdriver.com>