target/cortex_m: try to re-examine under reset in cortex_m_assert_reset()
An application often idling in real sleep mode may make a Cortex-M target
hard to access as CPU clock are gated and debug requests are responded
by WAIT ack.
Try to examine the target under reset as the last resort.
Change-Id: Ife875a966a838c37dde987bc584ad0a1f4d020d6
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7228
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>