ath11k: Fix target crash due to WBM_IDLE_LINK ring desc shortage

Make sure the number of WBM_IDLE_LINK ring descriptors is power
of 2. This increases the number of descriptors to 32k from the
current ~18k to fix the target assert because of the shortage in
the descriptors in WBM_IDLE_LINK ring. Remove unnecessary
power of 2 calculation in ath11k_dp_link_desc_setup() as it is
not required after this change.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>