m68k: merge the non-MMU and MMU versions of sigcontext.h

It is trivial to merge the non-MMU and MMU versions of sigcontext.h.
Without a single file "make headers_install" is broken for m68k
(since each of the sub-varients of sigconext.h are not installed).
Signed-off-by: Greg Ungerer <gerg@uclinux.org>

arch/m68k/include/asm/sigcontext.h

+#ifndef _ASM_M68k_SIGCONTEXT_H
+#define _ASM_M68k_SIGCONTEXT_H
+
+struct sigcontext {
+	unsigned long  sc_mask;		/* old sigmask */
+	unsigned long  sc_usp;		/* old user stack pointer */
+	unsigned long  sc_d0;
+	unsigned long  sc_d1;
+	unsigned long  sc_a0;
+	unsigned long  sc_a1;
 #ifdef __uClinux__
-#include "sigcontext_no.h"
-#else
-#include "sigcontext_mm.h"
+	unsigned long  sc_a5;
+#endif
+	unsigned short sc_sr;
+	unsigned long  sc_pc;
+	unsigned short sc_formatvec;
+#ifndef __uClinux__
+	unsigned long  sc_fpregs[2*3];  /* room for two fp registers */
+	unsigned long  sc_fpcntl[3];
+	unsigned char  sc_fpstate[216];
+#endif
+};
+
 #endif

arch/m68k/include/asm/sigcontext_mm.h

-#ifndef _ASM_M68k_SIGCONTEXT_H
-#define _ASM_M68k_SIGCONTEXT_H
-
-struct sigcontext {
-	unsigned long  sc_mask;		/* old sigmask */
-	unsigned long  sc_usp;		/* old user stack pointer */
-	unsigned long  sc_d0;
-	unsigned long  sc_d1;
-	unsigned long  sc_a0;
-	unsigned long  sc_a1;
-	unsigned short sc_sr;
-	unsigned long  sc_pc;
-	unsigned short sc_formatvec;
-	unsigned long  sc_fpregs[2*3];  /* room for two fp registers */
-	unsigned long  sc_fpcntl[3];
-	unsigned char  sc_fpstate[216];
-};
-
-#endif

arch/m68k/include/asm/sigcontext_no.h

-#ifndef _ASM_M68KNOMMU_SIGCONTEXT_H
-#define _ASM_M68KNOMMU_SIGCONTEXT_H
-
-struct sigcontext {
-	unsigned long  sc_mask; 	/* old sigmask */
-	unsigned long  sc_usp;		/* old user stack pointer */
-	unsigned long  sc_d0;
-	unsigned long  sc_d1;
-	unsigned long  sc_a0;
-	unsigned long  sc_a1;
-	unsigned long  sc_a5;
-	unsigned short sc_sr;
-	unsigned long  sc_pc;
-	unsigned short sc_formatvec;
-};
-
-#endif