armv7m: implement async algorithm functions

armv7m: implement async algorithm functions

Split armv7m_run_algorithm into two pieces and use them to reimplement it.
The arch_info parameter is used to keep context between the two calls, so
both calls must refer to the same armv7m_algorithm struct. Ugly but works
for a proof-of-concept.

Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>