[POWERPC][XEN] Provide _text for kexec.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>

--HG--
extra : transplant_source : %EB%19CNC%C0%B7%96%C8%14%B2%B0%91%9A%EB%3E%5E8P%C3

xen/arch/powerpc/xen.lds.S

@@ -17,6 +17,7 @@ PHDRS
 SECTIONS
 {
   . = 0x00400000;
+  PROVIDE(_text = .);
   /* Read-only sections, merged into text segment: */
   .interp         : { *(.interp) } :text
   .hash           : { *(.hash) }