csky: Fixup msa highest 3 bits mask

Just as comment mentioned, the msa format:

 cr<30/31, 15> MSA register format:
 31 - 29 | 28 - 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
   BA     Reserved  SH  WA  B   SO SEC  C   D   V

So we should shift 29 bits not 28 bits for mask

Signed-off-by: Liu Yibin <jiulong@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>