surfaceflinger: Fix legacy qcom display

This change: http://review.cyanogenmod.org/50222 disabled code
that is needed for legacy qcom using jb mr0 adreno blobs. Reenable
the needed code when qcom display variant is "legacy"

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: Ib36fb5388b941416e364db2109fdc7624a168563