[IA64] rename _bss to __bss_start

Rename _bss to __bss_start as on other architectures.  That makes it
possible to use the <linux/sections.h> instead of own declarations.  Also
add __bss_stop because that symbol exists on other architectures.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 00232b4..757e419 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -240,11 +240,12 @@
   .sdata : AT(ADDR(.sdata) - LOAD_OFFSET)
 	{ *(.sdata) *(.sdata1) *(.srdata) }
   _edata  =  .;
-  _bss = .;
+  __bss_start = .;
   .sbss : AT(ADDR(.sbss) - LOAD_OFFSET)
 	{ *(.sbss) *(.scommon) }
   .bss : AT(ADDR(.bss) - LOAD_OFFSET)
 	{ *(.bss) *(COMMON) }
+  __bss_stop = .;
 
   _end = .;