ARC: guard dsp early init against non ARCv2

As of today we guard early DSP init code with
ARC_AUX_DSP_BUILD (0x7A) BCR check to verify that we have
CPU with DSP configured. However that's not enough as in
ARCv1 CPU the same BCR (0x7A) is used for checking MUL/MAC
instructions presence.

So, let's guard DSP early init against non ARCv2.

Fixes: 4827d0cf ("ARC: handle DSP presence in HW")
Reported-by: Angelo Ribeiro <angelor@synopsys.com>
Suggested-by: Jose Abreu <oabreu@synopsys.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/dsp-impl.h

@@ -15,12 +15,14 @@
 
 /* clobbers r5 register */
 .macro DSP_EARLY_INIT
+#ifdef CONFIG_ISA_ARCV2
 	lr	r5, [ARC_AUX_DSP_BUILD]
 	bmsk	r5, r5, 7
 	breq    r5, 0, 1f
 	mov	r5, DSP_CTRL_DISABLED_ALL
 	sr	r5, [ARC_AUX_DSP_CTRL]
 1:
+#endif
 .endm
 
 /* clobbers r10, r11 registers pair */