wifi: ath11k: modify accessor macros to match index size

HE PHY is only 11 bytes, therefore it should be using byte indexes
instead of dword. Change corresponding macros to reflect this.

Signed-off-by: Muna Sinada <quic_msinada@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/1666128501-12364-2-git-send-email-quic_msinada@quicinc.com