Remove unnecessary deletion of OpenSSL intermediates from do_clean()

As changes in OpenSSL source automatically trigger a new OpenSSL
build when doing a clean build, there is no need to rebuild OpenSSL
on every clean build if there are no changes in OpenSSL source or
build-scripts. This change eliminates the unnecessary deletion of
OpenSSL intermediates from do_clean() and improves the build efficiency.

Signed-off-by: sahil <sahil@arm.com>
Change-Id: Icb28165b67dc7e5f1812a420ef0145acef4e1e9c