Build: Enable cppcheck under platform/ext/common.

The issues of cppcheck under platform/ext/common can be
found immediately.

Signed-off-by: Chendi Sun <chendi.sun@arm.com>
Change-Id: Ibd894a25b0e5cb6d18abc51a45fe6aa2355000f7
diff --git a/cppcheck/tfm-suppress-list.txt b/cppcheck/tfm-suppress-list.txt
index ca08f64..e93bf54 100644
--- a/cppcheck/tfm-suppress-list.txt
+++ b/cppcheck/tfm-suppress-list.txt
@@ -48,7 +48,10 @@
 *:*/docs/*
 *:*/tools/*
 *:*/bl2/ext/*
-*:*/platform/ext/*
+*:*/platform/ext/accelerator/*
+*:*/platform/ext/cmsis/*
+*:*/platform/ext/driver/*
+*:*/platform/ext/target/*
 *:*/mcuboot/*
 *:*/mbedtls/*
 *:lib/ext/qcbor-src/*