ADIv5 clean up AP fault handling

ADIv5 clean up AP fault handling

Pass up fault codes from various routines, so their callers
can clean up after failures, and remove the FIXME comments
highlighting those previously goofy code paths.

 dap_ap_{read,write}_reg_u32()
 dap_ap_write_reg()
 mem_ap_{read,write}_u32()
 mem_ap_{read,write}_atomic_u32()
 dap_setup_accessport()

Make dap_ap_write_reg_u32() just wrap dap_ap_write_reg(),
instead of cloning its core code (and broken fault handling).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>