ARM11: don't expose DSCR

ARM11: don't expose DSCR

Remove the remaining extra copy of DSCR, and the register cache
of which it was a part.  That cache wasn't a very safe, or even
necessary, idea; it was essentialy letting debugger-private state
be manipulated by Tcl code that couldn't know how to do it right.

This makes the "reg" output of an ARM11 resemble what most other
ARM cores produce ... forward motion in the "make ARM11 work like
the rest of the ARM cores" Jihad!