ov7670: clean up ov7670_read semantics

ov7670: clean up ov7670_read semantics

commit bca5c2c550f16d2dc2d21ffb7b4712bd0a7d32a9 upstream

Cortland Setlow pointed out a bug in ov7670.c where the result from
ov7670_read() was just being checked for !0, rather than <0.  This made me
realize that ov7670_read's semantics were rather confusing; it both fills
in 'value' with the result, and returns it.  This is goes against general
kernel convention; so rather than fixing callers, let's fix the function.

This makes ov7670_read return <0 in the case of an error, and 0 upon
success. Thus, code like:

res = ov7670_read(...);
if (!res)
	goto error;

.will work properly.

Signed-off-by: Cortland Setlow <csetlow@tower-research.com>
Signed-off-by: Andres Salomon <dilinger@debian.org>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>