dload_util: Add normal dload mode entrance

Enum determines if the requested dload mode is emergency or normal.
All dependent function calls are updated respectively.
msm8974 and msm8226 set_download_mode() functions are updated with the
target-specific normal download mode address

Change-Id: I500c1e3c7e835ad6a6fa59ea2701790a7fd12769
diff --git a/target/msm8226/init.c b/target/msm8226/init.c
index ac648e8..026aa53 100644
--- a/target/msm8226/init.c
+++ b/target/msm8226/init.c
@@ -328,9 +328,10 @@
 	return _emmc_recovery_init();
 }
 
-int set_download_mode(void)
+int set_download_mode(enum dload_mode mode)
 {
-	dload_util_write_cookie(FORCE_DLOAD_MODE_ADDR);
+	dload_util_write_cookie(mode == NORMAL_DLOAD ?
+		DLOAD_MODE_ADDR : EMERGENCY_DLOAD_MODE_ADDR, mode);
 
 	return 0;
 }