soc: qcom: smem: Rename "uncached" accessors

In preparation for adding accessors for "cached" entries rename the
"uncached" accessors. Also rename "first" cached entry to "last", as
the cached list grows backwards.

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>