Revert "GCC: Upgrade to version 9.2-2019.12 of toolchain"

This reverts commit de9bf1d8a2de952bfc17cdf7082b41f9c185e54d.

Change-Id: Iebb6297ce290a10ee850bf6a9c71e7eb530b085f
diff --git a/docs/plat/poplar.rst b/docs/plat/poplar.rst
index 040b593..215f551 100644
--- a/docs/plat/poplar.rst
+++ b/docs/plat/poplar.rst
@@ -68,7 +68,7 @@
 
 .. code:: bash
 
-       make CROSS_COMPILE=aarch64-none-elf- all fip SPD=none PLAT=poplar
+       make CROSS_COMPILE=aarch64-linux-gnu-  all fip SPD=none PLAT=poplar
        BL33=u-boot.bin
 
 -  Build l-loader (generated the final fastboot.bin)