m68k: Kill several external declarations in source files

- Replace external declarations by proper includes where availiable.
    The accesses to some symbols had to be modified, as before they were
    declared using e.g. "extern int _end", while asm-generic/sections.h uses
    e.g. "extern char _end[]"
  - Remove unused or superfluous external declarations

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/mvme147/config.c

@@ -42,7 +42,6 @@ extern unsigned long mvme147_gettimeoffset (void);
 extern int mvme147_hwclk (int, struct rtc_time *);
 extern int mvme147_set_clock_mmss (unsigned long);
 extern void mvme147_reset (void);
-extern void mvme147_waitbut(void);
 
 
 static int bcd2int (unsigned char b);