ARM: Fix the ldscripts so that exit/enter stage work correctly.

Remove the spurious creation of a start symbol, and use the
stage_entry symbol directly.

Change-Id: Ia62d5c056ac8b20c8ffdb78bff3d306065b6c45f
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/2560
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)

src/arch/armv7/coreboot_ram.ld

@@ -22,7 +22,7 @@
 /* We use ELF as output format. So that we can debug the code in some form. */
 INCLUDE ldoptions
 
-ENTRY(_start)
+ENTRY(stage_entry)
 
 SECTIONS
 {

src/arch/armv7/romstage.ld

@@ -28,7 +28,7 @@
 OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
 OUTPUT_ARCH(arm)
 
-ENTRY(_start)
+ENTRY(stage_entry)
 
 SECTIONS
 {