qcacmn: Reduce CE4 source ring entries number

For lithium based HST/HSP, CE4 is no longer used for data TX,
just few HTT msg for ring configuration, 2048 entries requires
16 * 2048 = 32K ring consistent memory which looks is not necessary,
reduce CE4 ring entries number to 256.

Change-Id: I117ec81cbee3642d640457c37a7ab900ddcae3f5
CRs-Fixed: 2757925