ARM: dts: msm: Make SPSS heap a secure CMA heap

Currently the SPSS heap is defined as a CMA heap for sdm855 however it
should be defined as a secure CMA heap so fix this.

Change-Id: I6d554519a0eec83ff3165f807797a71df424ec6e
Signed-off-by: Liam Mark <lmark@codeaurora.org>