py: Fix mp_obj_t -> mp_const_obj_t for mp_obj_int_get_checked()

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
Merge pull request #615 from swegener/for-upstream

py: Fix mp_obj_t -> mp_const_obj_t for mp_obj_int_get_checked()
stmhal: Activate bootloader with pyb.bootloader()

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
stmhal: Remap system flash and adjust addresses

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
Merge pull request #618 from swegener/jump-to-bootloader

Jump to bootloader
stmhal: Make pyb.bootloader take no arguments.
stmhal: Fix write_timed function for DAC(2).

Addresses issue #617.