Fix SAMA5 vector linking issue

arch/arm/src/armv7-a/arm_vectortab.S

@@ -58,7 +58,8 @@
  *   Vector initialization block
  ****************************************************************************/
 
-	.globl	_vector_start
+	.section	.vectors, "ax"
+	.globl		_vector_start
 
 /* These will be relocated to VECTOR_BASE. */
 

configs/sama5d3x-ek/scripts/ddram.ld

@@ -56,7 +56,7 @@ SECTIONS
 {
 	.text : {
 		_stext = ABSOLUTE(.);
-		*(.vectors)
+		KEEP (*(.vectors))
 		*(.text .text.*)
 		*(.fixup)
 		*(.gnu.warning)

configs/sama5d3x-ek/scripts/isram.ld

@@ -53,7 +53,7 @@ SECTIONS
 {
 	.text : {
 		_stext = ABSOLUTE(.);
-		*(.vectors)
+		KEEP (*(.vectors))
 		*(.text .text.*)
 		*(.fixup)
 		*(.gnu.warning)

configs/sama5d3x-ek/scripts/pg-sram.ld

@@ -81,7 +81,7 @@ SECTIONS
 {
 	.locked : {
 		_slocked = ABSOLUTE(.);
-		*(.vectors)
+		KEEP (*(.vectors))
 		up_head.o locked.r (.text .text.*)
 		up_head.o locked.r (.fixup)
 		up_head.o locked.r (.gnu.warning)