ARC: ARCv2: handle DSP presence in HW

In case of DSP extension presence in HW some instructions
(related to integer multiply, multiply-accumulate, and divide
operation) executes on this DSP execution unit. So their
execution will depend on dsp configuration register (DSP_CTRL)
As we want these instructions to execute the same way regardless
of DSP presence we need to set DSP_CTRL properly.

NOTE:
we do the same adjustments in Linux kernel, see in kernel tree:
commit 4827d0cf744e ("ARC: handle DSP presence in HW")

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index fff6591..f3cd4a8 100644
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -100,6 +100,7 @@
 
 /* DSP-extensions related auxiliary registers */
 #define ARC_AUX_DSP_BUILD	0x7A
+#define ARC_AUX_DSP_CTRL	0x59F
 
 /* ARC Subsystems related auxiliary registers */
 #define ARC_AUX_SUBSYS_BUILD	0xF0