ath10k: fix line length warning in ath10k_ce_alloc_dest_ring()

Commit 750afb08

 ("cross-tree: phase out dma_zalloc_coherent()") introduced
a new checkpatch warning:

drivers/net/wireless/ath/ath10k/ce.c:1602: line over 90 characters

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