err.h: remove deprecated PTR_RET for good

err.h: remove deprecated PTR_RET for good

Initially, commit 56ca32aab1f7 ("include/linux/err.h: add a function to
cast error-pointers to a return value") from Uwe Kleine-König introduced
PTR_RET in 03/2011. Then, in 07/2013, commit 109b419699b4 ("PTR_RET is
now PTR_ERR_OR_ZERO") from Rusty Russell renamed PTR_RET to
PTR_ERR_OR_ZERO, and left PTR_RET as deprecated-marked alias.

After six years since the renaming and various repeated cleanups in the
meantime, it is time to finally remove the deprecated PTR_RET for good.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>