Introduce generic shutdown_free() and remove redundant internal_shutdown().

The former will be useful in cases where cleanup equals a simple call to free().

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>

git-svn-id: svn://flashrom.org/flashrom/trunk@1848 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1