qcacmn: Add prefetch_timer config for CE rings

Add prefetch_timer configuration for CE rings.
Set prefetch_timer=1 configuration for qca6490 destination CEs,
prefetch_timer=0 configuration for other targets CEs..
Basically setting to 1us asking CE hw to update ring tail pointer to
update within 1us. FW side CE SW sets all rings to 1us already.
Idea behind this change  is, we have seen pre-silicon issue where SRC
ring TP read by SW was not seen updated value when prefetch was set
to 8us. Changing prefetch timer value to 1us helps to resolve
pre-silicon issue.
So host side rings need to update the prefetch timer to 1us.

Change-Id: I0830c73517c29cf39e6b2974bf3faa44e5673741
CRs-Fixed: 2669762