SPR's CFAR, DEC, HDEC, TB-L/U are not implemented as part of CPUPPCState.
Hence, gdbstub is not able to access them using (CPUPPCState *)env->spr[] array.
Update gdb_get_spr_reg() method to handle these SPR's specifically.
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Saif Abrar <saif.abrar@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>