fix(check-include-order): put include/plat/common in project files

This issue was reported in [1]. It follows some static check failed
when pushing patch [2], for which CI reported static check failure
in [3].
As files in include/plat/common directory are common to all platforms,
consider them as project files, and not platform files.

[1] https://lists.trustedfirmware.org/pipermail/tf-a/2021-September/001316.html
[2] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/10662
[3] https://ci.trustedfirmware.org/job/tf-static-checks/1192/

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: Ie0de4dd5ed6dc03ab0fd695ad9b8169134f79964
diff --git a/script/static-checks/check-include-order.py b/script/static-checks/check-include-order.py
index aaf84f1..53d355b 100755
--- a/script/static-checks/check-include-order.py
+++ b/script/static-checks/check-include-order.py
@@ -87,6 +87,8 @@
     incs = collections.defaultdict(list)
     error_msgs = []
     plat_incs = dir_include_paths("plat") | dir_include_paths("include/plat")
+    plat_common_incs = dir_include_paths("include/plat/common")
+    plat_incs.difference_update(plat_common_incs)
     libc_incs = dir_include_paths("include/lib/libc")
 
     for inc in inc_list: