When controlled from a debugger (build with INCLUDE_GDB_CONTROL macro);
when stopped due a EBREAK instruction; on a 'resume' command ('continue' in GDB),
was getting stuck. This is now working.
At this point, all debugger functionality (almost: see below) is working:
halt, step, breakpoints, resume, read/write gpr/fpr/csr, read/write memory.
Still todo: "NDM reset" (non-debug module reset).
Stop, set breakpoint: working, stopping successfully.
Step: working: stops after a step.
Continue (resume) working after Stop and Step, but not after stop by breakpoint (needs debugging)
Read/Write GPRs, FPRs, CSRs, memory working.
New method 'debug_external_interrupt_req' to support emulation of a
debug module starts at P3_Core interface and is plumbed all the way in
to the CSR register MIP as interrupt [14]. The corresponding MIE[14]
is always 1, so it is never masked. Still todo: should not be masked
by MSTATUS interrupt-enables either. Also expanded
interrupt-detection logic, mcause etc. to extend up to interrupt 14.
Builds in standalone mode, runs ISA tests.
Builds in src_SSITH_P3, generating RTL.
