FRV: Fix incorrect symbol in copy_thread()

Fix an incorrect symbol in copy_thread():

  arch/frv/kernel/process.c: In function 'copy_thread':
  arch/frv/kernel/process.c:197: error: 'chilregs' undeclared (first use in this function)
  arch/frv/kernel/process.c:197: error: (Each undeclared identifier is reported only once
  arch/frv/kernel/process.c:197: error: for each function it appears in.)

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>