powerpc/cell: set no_llseek in spufs_cntl_fops

In spufs_cntl_fops, since we use nonseekable_open() to open, we
should use no_llseek() to seek, not generic_file_llseek().

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>