MIPS: SNI: Fix GCC 4.6.0 build error

  CC      arch/mips/sni/time.o
arch/mips/sni/time.c: In function 'dosample':
arch/mips/sni/time.c:98:19: error: variable 'lsb' set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>