m68k: Fix relocation errors in start.S

When the environment sectors in the flash are big, one get those errors :

 mcf547x_8x/start.S:173: relocation truncated to fit: R_68K_PC16 against
  symbol `cpu_init_f' defined in .text section in libmcf547x_8x.a(cpu_init.o)
 mcf547x_8x/start.S:174: relocation truncated to fit: R_68K_PC16 against
  symbol `board_init_f' defined in .text section in libm68k.a(board.o)

Fix that.

Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Cc: "Jin Zhengxiong-R64188" <R64188@freescale.com>
Cc: Jason Jin <jason.jin@freescale.com>

arch/m68k/cpu/mcf547x_8x/start.S

@@ -164,8 +164,8 @@ _start:
 
 	move.l #__got_start, %a5	/* put relocation table address to a5 */
 
-	bsr cpu_init_f			/* run low-level CPU init code (from flash) */
-	bsr board_init_f		/* run low-level board init code (from flash) */
+	jbsr cpu_init_f			/* run low-level CPU init code (from flash) */
+	jbsr board_init_f		/* run low-level board init code (from flash) */
 
 	/* board_init_f() does not return */