ath10k: rename HTC_HOST_MAX_MSG_PER_BUNDLE define

This define is only used for RX bundling so it is more descriptive if
RX is added to the define-name.

Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>