treewide: Add missing includes ...

Many files in the tree implement functions, but do not include the
header files which provide the prototypes for these functions. This
means conflicting prototypes remain undetected. Add the missing
includes.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

keystore: implement forgetting secrets ...

To be able to change secrets add a function to forget secrets.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

crypto: add simple keystore ...

This patch adds a simple keystore to barebox. The keystore implements a simple
key-value store to hold arbitrary values.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>