mfd: always assign of_node in mfd_add_device()

mfd_add_device() assigns .of_node in the device objects it creates only
if the mfd_cell for the device has the .of_compatible field set and the
DT node for the top-level MFD device contains a child whose compatible
property matches the cell's .of_compatible field.

This leaves .of_node unset in many cases. When this happens, entries in
the DT /aliases property which refer to the top-level MFD DT node will
never match the MFD child devices, hence causing the requested alias not
to be honored.

Solve this by setting each MFD child device's .of_node equal to the top-
level MFD device's .of_node field in the cases where it would otherwise
remain unset.

The first use-case for this will be aliases for the TPS6586x's RTC
device.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
The 3 patches in this series are all independent; they can be applied
to their respective subsystems in any order. I'm simply posting them as
a series to make the use-case more obvious.
rtc: honor device tree /alias entries when assigning IDs

Assign RTC device IDs based on device tree /aliases entries if present,
falling back to the existing numbering scheme if there is no /aliases
entry (which includes when the system isn't booted using DT), or there
is a numbering conflict.

This is useful in systems with multiple RTC devices, to ensure that the
best RTC device is selected as /dev/rtc0, which provides the overall
system time.

For example, Tegra has an on-SoC RTC that is not battery backed,
typically coupled with an off-SoC RTC that is battery backed. Only the
latter is useful for populating the system time, yet the former is
useful e.g. for wakeup timing, since the time is not lost when the
system is sleeps.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
The 3 patches in this series are all independent; they can be applied
to their respective subsystems in any order. I'm simply posting them as
a series to make the use-case more obvious.
ARM: tegra: set up /aliases entries for RTCs

This ensures that the PMIC RTC provides the system time, rather than
the on-SoC RTC, which is not battery-backed.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
This patch is just an example. If the previous two patches are accepted,
I'll flesh this patch out to cover all boards, and repost.