st/nine: fix the swizzle for ATI1 / PIPE_FORMAT_RGTC1_UNORM.

Signed-off-by: Xavier Bouchoux <xavierb@gmail.com>
Merge pull request #44 from xxxbxxx/for-upstream-2

st/nine: fix the swizzle for ATI1 / PIPE_FORMAT_RGTC1_UNORM.