target/hla_target: set cortex_m->common_magic

target/hla_target: set cortex_m->common_magic

hla_target uses the same struct cortex_m_common as the standard cortex_m
target. Unlike the cortex_m target hla missed setting of common_magic.

Set commont_magic to help pointer verification.

Add convenience tests is_cortex_m_or_hla() and
is_cortex_m_with_dap_access()

Use proper test in cortex_m_verify_pointer() - this code relied on
unset common_magic on hla target before the change.

Change-Id: I4dae79f056c3d73adf524e26aa8ef2d3a57b471e
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6741
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>