media: docs: v4l2grab.c.rst: change unintended assignment

Example should be comparing errno to EINTR instead of doing assignment.
Signed-off-by: Daniel Lundberg Pedersen <dlp@qtec.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/userspace-api/media/v4l/v4l2grab.c.rst

@@ -134,7 +134,7 @@ file: media/v4l/v4l2grab.c
 			    tv.tv_usec = 0;
 
 			    r = select(fd + 1, &fds, NULL, NULL, &tv);
-		    } while ((r == -1 && (errno = EINTR)));
+		    } while ((r == -1 && (errno == EINTR)));
 		    if (r == -1) {
 			    perror("select");
 			    return errno;