armv8_dpm_get_core_state() function

@file Implements various ARM DPM operations using architectural debug registers. These routines layer over core-specific communication methods to cope with implementation differences between cores like ARM1136 and Cortex-A8. The "Debug Programmers' Model" (DPM) for ARMv6 and ARMv7 is defined by Part C (Debug Architecture) of the ARM Architecture Reference Manual, ARMv7-A and ARMv7-R edition (ARM DDI 0406B). In OpenOCD, DPM operations are abstracted through internal programming interfaces to share code and to minimize needless differences in debug behavior between cores. Get core state from EDSCR, without necessity to retrieve CPSR