[packaging] drop yaml and just use spec

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[sb2] get rid of own sb2 modes and just symlink to obs-rpm-* modes

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[mb2] set build target correctly to i486

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>