udmabuf: set read/write flag when exporting

Otherwise, mmap fails when done with PROT_WRITE.

Suggested-by: Gurchetan Singh <[e-mail]>
Signed-off-by: Gerd Hoffmann <[e-mail]>
Reviewed-by: Gurchetan Singh <[e-mail]>
Tested-by: Gurchetan Singh <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/dma-buf/udmabuf.c

···
 	exp_info.ops  = &udmabuf_ops;
 	exp_info.size = ubuf->pagecount << PAGE_SHIFT;
 	exp_info.priv = ubuf;
+	exp_info.flags = O_RDWR;
 
 	buf = dma_buf_export(&exp_info);
 	if (IS_ERR(buf)) {