soc: qcom: smem: Support getting cached entries

On msm8996 cached SMEM items are used for storing the GLINK FIFOs, so
for items not found in the uncached list we need to also search the
cased list for these items.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
(cherry picked from commit c7c1dc35)