Refine target description register types+groups
Refine target description register types+groups

* Explicitly label FP registers as 'ieee_double' and 'ieee_float'.
* Mark msp and psp as 'data_ptr' type like sp.
* Assign msp, psp, primask, control, basepri and faultmask to 'system'
  group.

Not sure if FP type change has any affect, but is consistent with XML
in GDB.

Marking msp and psp as "data_ptr" means that "info register psp" will
show a symbol match like "<_main_stack+4080>", as it does with sp.

Making other registers system means they can be shown with "info
registers system". However, it doesn't currently remove them from "info
registers" or "info registers general" - these both appear to have
hard-coded behaviour of showing all non-vector non-float registers, not
specifically "general" ones. The intent is that only r0-12,sp,lr,pc,xpsr
would be shown in general, if GDB were to obey that label as some
documentation suggests.

pyocd/pyOCD,mbedmicro/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mesheven/pyOCD,flit/pyOCD,mbedmicro/pyOCD,pyocd/pyOCD,mesheven/pyOCD,mesheven/pyOCD