dma-buf: remove useless FMODE_LSEEK flag

This is already set by anon_inode_getfile(), since dma_buf_fops has
non-NULL ->llseek, so we don't need to set it here too.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>