classes: bundle: Add keyring file argument
classes: bundle: Add keyring file argument

Add an argument for specifying the keyring file used for bundle
signature verification.

Signed-off-by: Martin Schwan <0b4b17d835f86924185dc5770bd021250822e547@phytec.de>

rauc/meta-rauc,rauc/meta-rauc,rauc/meta-rauc,rauc/meta-rauc