Refurbish arc_elf_object_p() function

Conflicts:
	bfd/ChangeLog.ARC
Handle .nt/.t flag only for ARCv2
Add DSYNC, WEVT, and WLFC instructions
Add DMB instruction
Disassemble DMB and DSYNC

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>