linux err: make ERR_PTR/PTR_ERR architecture specific

linux err: make ERR_PTR/PTR_ERR architecture specific

This patch changes ERR_PTR/PTR_ERR to use CONFIG_ERR_PTR_OFFSET to map
errno values into a pointer region that cannot contain valid pointers.

IS_ERR and IS_ERR_OR_NULL have to be converted to use PTR_ERR, too,
for this to work.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>