ARM: dts: msm8974: Remove "unused" reserved region

sources for msm8974, this isn't actually a reserved region.
Instead it's marked as "unused" for reserved regions. Let's
remove it so we get back a good chunk of memory.

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>