arm: fix incorrect monitor protection region in FLASH

Monitor protection region in FLASH did not cover .rel.dyn
and .dynsym sections, because it uses __bss_start to compute
monitor_flash_len. Use _end instead.

Add _end to linker scripts for end of u-boot image
Add _end_ofs to all the start.S.

Signed-off-by: Po-Yu Chuang <ratbert@faraday-tech.com>
diff --git a/arch/arm/cpu/arm946es/start.S b/arch/arm/cpu/arm946es/start.S
index 1b6b188..00914f4 100644
--- a/arch/arm/cpu/arm946es/start.S
+++ b/arch/arm/cpu/arm946es/start.S
@@ -105,6 +105,10 @@
 _bss_end_ofs:
 	.word __bss_end__ - _start
 
+.globl _end_ofs
+_end_ofs:
+	.word _end - _start
+
 #ifdef CONFIG_USE_IRQ
 /* IRQ stack memory (calculated at run-time) */
 .globl IRQ_STACK_START