Makefile: remove extra include paths in INCLUDES

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

Commit 09d40e0e ("Sanitise includes across codebase") provides more
information.

Change-Id: Ifedc79d9f664d208ba565f5736612a3edd94c647
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>