src/bootchooser: prefix all error messages with backend used
src/bootchooser: prefix all error messages with backend used

This prepends all bootchooser backend error messages with the name of
the backend actually used. This eases identifying if the right one is
used and where/why it failed.

Signed-off-by: Enrico Joerns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

rauc/rauc,ejoerns/rauc,jluebbe/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc