ia64/unaligned: Silence another GCC warning about an uninitialised variable

  arch/ia64/kernel/unaligned.c: In function 'ia64_handle_unaligned':
  arch/ia64/kernel/unaligned.c:1385:16: warning: 'u.l' may be used uninitialized in this function [-Wmaybe-uninitialized]
    opcode = (u.l >> IA64_OPCODE_SHIFT) & IA64_OPCODE_MASK;
                ^

Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Tony Luck <tony.luck@intel.com>