mhi: core: Resolve issue for UL/DL

Resolve issue whereby UL DL properties were
being incorrectly set for non HW event rings.

CRs-Fixed: 827294
Change-Id: Ie279061e84c0f2498393c5d7bfaef404307c84da
Signed-off-by: Andrei Danaila <adanaila@codeaurora.org>
Signed-off-by: Tony Truong <truong@codeaurora.org>