sm7250-common: Force triple frame buffers

* This yields significantly reduced jitter and doesn't have any measurable impact on latency.

Signed-off-by: DarkAngelGR <asavvo01@gmail.com>

system.prop

@@ -33,6 +33,7 @@ debug.gralloc.gfx_ubwc_disable=0
 debug.sf.enable_hwc_vds=1
 debug.sf.latch_unsignaled=1
 persist.vendor.color.matrix=2
+ro.surface_flinger.max_frame_buffer_acquired_buffers=3
 
 # CNE
 persist.vendor.cne.feature=1