scripts: set proper OpenSSL include dir also for sign-file

commit fe968c41ac4f4ec9ffe3c4cf16b72285f5e9674f upstream.

Fixes: 2cea4a7a1885 ("scripts: use pkg-config to locate libcrypto")
Signed-off-by: Rolf Eike Beer <eb@emlix.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>