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/arm920t/ep93xx/u-boot.lds b/arch/arm/cpu/arm920t/ep93xx/u-boot.lds
index 4cc82a5..dc6ba34 100644
--- a/arch/arm/cpu/arm920t/ep93xx/u-boot.lds
+++ b/arch/arm/cpu/arm920t/ep93xx/u-boot.lds
@@ -56,4 +56,6 @@
 	__bss_start = .;
 	.bss : { *(.bss) }
 	__bss_end__ = .;
+
+	_end = .;
 }