signals: demultiplexing SIGTRAP signal, fix

fix build breakage, missing header file.
Signed-off-by: NSrinivasa DS <srinivasa@in.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/asm-x86/traps.h

 #ifndef ASM_X86__TRAPS_H
 #define ASM_X86__TRAPS_H
 
+#include <asm/debugreg.h>
+
 /* Common in X86_32 and X86_64 */
 asmlinkage void divide_error(void);
 asmlinkage void debug(void);