ath9k_hw: Fix opmode initialization

ath9k_hw: Fix opmode initialization

Commit "ath9k_hw: Relocate Opmode initialization"
moved the opmode initialization before the STA_ID1 register
was programmed with defaults. This changed the original
behaviour because the re-programming code doesn't take into
account the existing value in the register. Both ath9k and ath9k_htc
were not affected by this change because the opmode is
re-initialized after every reset, when RX is started.

Revert to the original behavior, except keep it outside the
REGWRITE block. This would help remove extraneous opmode calls
in the driver core.

Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>