target: 8909: Fix SPI code compatibility with non-spi targets

Add DISPLAY_TYPE_SPI_SUPPORT flag which can be used to avoid
compilation error in targets which doesn't use SPI display.

Change-Id: Ic41dd56b422cd511205c0f0ea8acf7c0eb65ca37
diff --git a/target/msm8909/rules.mk b/target/msm8909/rules.mk
index 1550990..2fb3413 100644
--- a/target/msm8909/rules.mk
+++ b/target/msm8909/rules.mk
@@ -14,6 +14,7 @@
 DEFINES += DISPLAY_TYPE_MIPI=1
 DEFINES += DISPLAY_TYPE_DSI6G=1
 DEFINES += NO_ALARM_DISPLAY=0
+DEFINES += DISPLAY_TYPE_SPI_SUPPORT=1
 
 MODULES += \
 	dev/keys \