ARC: Rely on compiler generated macros to segregate ARCompact/ARCv2 code

Use the .config items only to select the right ISA option for gcc/gas

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
ARC/ldso: __udivmodsi4() not available for ARCv2

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
ARCv2/ldso: Add ELF Magic

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