mem_ap: fix GDB connections
After commit
d9b2607ca094 ("gdb_server: support sparse register
maps"), GDB crashes while requesting the value of 'cpsr' because
the fake register is tagged as not existing.
Change the logic and set all register as existing, while still
limiting the list for the initial GDB request at connect.
Change-Id: I1c4e274c06147683db2a59a8920ae5ccd863e15c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8163
Tested-by: jenkins