fwu: provide default fwu_plat_get_bootidx

Just like fwu_plat_get_update_index, provide a default/weak
implementation of fwu_plat_get_bootidx. So that most platforms
wouldn't have to re-implement the likely case.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
1 file changed