Merge branch 'of_get_mac_address-ERR_PTR-fixes'

Petr Štetiar says:

====================
of_get_mac_address ERR_PTR fixes

this patch series is an attempt to fix the mess, I've somehow managed to
introduce.

First patch in this series is defacto v5 of the previous 05/10 patch in the
series, but since the v4 of this 05/10 patch wasn't picked up by the
patchwork for some unknown reason, this patch wasn't applied with the other
9 patches in the series, so I'm resending it as a separate patch of this
fixup series again.

Second patch is a result of this rebase against net-next tree, where I was
checking again all current users of of_get_mac_address and found out, that
there's new one in DSA, so I've converted this user to the new ERR_PTR
encoded error value as well.

Third patch which was sent as v5 wasn't considered for merge, but I still
think, that we need to check for possible NULL value, thus current IS_ERR
check isn't sufficient and we need to use IS_ERR_OR_NULL instead.

Fourth patch fixes warning reported by kbuild test robot.
====================

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>