m68k: Fix wrong assembler instruction in start.S

The jmp _fault generated the following error message, thus change it
to bra _fault:

start.S: Assembler messages:
start.S:310: Error: Conversion of PC relative displacement to absolute

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: "Jin Zhengxiong-R64188" <R64188@freescale.com>
Cc: Jason Jin <jason.jin@freescale.com>

arch/m68k/cpu/mcf5227x/start.S

@@ -485,7 +485,7 @@ clear_bss:
 /* exception code */
 	.globl _fault
 _fault:
-	jmp _fault
+	bra _fault
 	.globl	_exc_handler
 
 _exc_handler:

arch/m68k/cpu/mcf523x/start.S

@@ -247,7 +247,7 @@ clear_bss:
 /* exception code */
 	.globl _fault
 _fault:
-	jmp _fault
+	bra _fault
 	.globl	_exc_handler
 
 _exc_handler:

arch/m68k/cpu/mcf52x2/start.S

@@ -307,7 +307,7 @@ clear_bss:
 /* exception code */
 	.globl _fault
 _fault:
-	jmp _fault
+	bra _fault
 
 	.globl	_exc_handler
 _exc_handler:

arch/m68k/cpu/mcf532x/start.S

@@ -261,7 +261,7 @@ clear_bss:
 /* exception code */
 	.globl _fault
 _fault:
-	jmp _fault
+	bra _fault
 	.globl	_exc_handler
 
 _exc_handler: