MN10300: Add missing _sdata declaration

_sdata needs to be declared in the linker script now as of commit
a2d063ac216c ("extable, core_kernel_data(): Make sure all archs define
_sdata")

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/mn10300/kernel/vmlinux.lds.S

@@ -44,6 +44,7 @@ SECTIONS
   RO_DATA(PAGE_SIZE)
 
   /* writeable */
+  _sdata = .;     /* Start of rw data section */
   RW_DATA_SECTION(32, PAGE_SIZE, THREAD_SIZE)
   _edata = .;