sparc32: fix fallout from system.h removal

Build failures for the typical configs I use

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/include/asm/ptrace.h b/arch/sparc/include/asm/ptrace.h
index 9835adc..fd9c3f2 100644
--- a/arch/sparc/include/asm/ptrace.h
+++ b/arch/sparc/include/asm/ptrace.h
@@ -241,6 +241,7 @@
 #ifndef __ASSEMBLY__
 
 #ifdef __KERNEL__
+#include <asm/switch_to.h>
 
 static inline bool pt_regs_is_syscall(struct pt_regs *regs)
 {