ath9k: remove needless NFCAL_PENDING flag setting

The NFCAL_PENDING flag is set by the ath9k_hw_start_nfcal() routine,
so there is no reason to set it manually after calling it during the
AR9002 calibrations initialization.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200424004923.17129-3-ryazanov.s.a@gmail.com