ARC: add support for DSP-enabled userspace applications

To be able to run DSP-enabled userspace applications we need to
save and restore following DSP-related registers:
At IRQ/exception entry/exit:
 * DSP_CTRL (save it and reset to value suitable for kernel)
 * ACC0_LO, ACC0_HI (we already save them as r58, r59 pair)
At context switch:
 * ACC0_GLO, ACC0_GHI
 * DSP_BFLY0, DSP_FFT_CTRL

Reviewed-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index ec532d1..0fcea5b 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -14,6 +14,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/ptrace.h>
+#include <asm/dsp.h>
 #include <asm/fpu.h>
 
 #ifdef CONFIG_ARC_PLAT_EZNPS
@@ -31,6 +32,9 @@ struct thread_struct {
 	unsigned long ksp;	/* kernel mode stack pointer */
 	unsigned long callee_reg;	/* pointer to callee regs */
 	unsigned long fault_address;	/* dbls as brkpt holder as well */
+#ifdef CONFIG_ARC_DSP_SAVE_RESTORE_REGS
+	struct dsp_callee_regs dsp;
+#endif
 #ifdef CONFIG_ARC_FPU_SAVE_RESTORE
 	struct arc_fpu fpu;
 #endif