ath10k: remove unused member in ath10k_hw_regs

rtc_state_cold_reset_mask is unused in ath10k_hw_regs.
instead fixed delays are used.

Signed-off-by: Anilkumar Kolli <akolli@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>