compat: backport PTR_RET()

compat: backport PTR_RET()

mcgrof@frijol ~/linux-next (git::master)$ git describe --contains fa9ee9c4
v2.6.39-rc1~267

commit fa9ee9c4b9885dfdf8eccac19b8b4fc8a7c53288
Author: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Date:   Tue Mar 22 16:34:05 2011 -0700

    include/linux/err.h: add a function to cast error-pointers to a return value

    PTR_RET() can be used if you have an error-pointer and are only interested
    in the eventual error value, but not the pointer.  Yields the usual 0 for
    no error, -ESOMETHING otherwise.

    Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>