Makefile: remove extra include paths in INCLUDES

Now it is needed to use the full path of the common header files.

Commit 09d40e0e0828 ("Sanitise includes across codebase") provides more
information.

Change-Id: Ifedc79d9f664d208ba565f5736612a3edd94c647
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/plat/imx/common/imx_sip_handler.c b/plat/imx/common/imx_sip_handler.c
index 55639cd..4eabda7 100644
--- a/plat/imx/common/imx_sip_handler.c
+++ b/plat/imx/common/imx_sip_handler.c
@@ -6,7 +6,7 @@
 
 #include <stdlib.h>
 #include <stdint.h>
-#include <std_svc.h>
+#include <services/std_svc.h>
 #include <string.h>
 #include <platform_def.h>
 #include <common/debug.h>