include 'path/to' prefix when specifying tftf.bin on make fip cmd

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I7c316acd486346332403c758f632147ab71c48f2
diff --git a/docs/getting_started/build.rst b/docs/getting_started/build.rst
index f137afe..27ad580 100644
--- a/docs/getting_started/build.rst
+++ b/docs/getting_started/build.rst
@@ -99,7 +99,7 @@
 
 ::
 
-    BL33=tftf.bin make PLAT=<platform> fip
+    BL33=<path/to/tftf.bin> make PLAT=<platform> fip
 
 Please refer to the `TF-A documentation`_ for further details.