ath10k: add bmi_read32/bmi_write32 functions

Add ath10k_bmi_read32/ath10k_bmi_write32 functions
and use them in core layer when read32/write32.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>