ARM: dts: Fix incomplete dts data for am3 and am4 mmc

Commit 4e27f752 ("ARM: OMAP2+: Drop mmc platform data for am330x and
am43xx") dropped legacy mmc platform data for am3 and am4, but missed the
fact that we never updated the dts files for mmc3 that is directly on l3
interconnect instead of l4 interconnect. This leads to a situation with
no legacy platform data and incomplete dts data.

Let's update the mmc instances on l3 interconnect to probe properly with
ti-sysc interconnect target module driver to make mmc3 work again. Let's
still keep legacy "ti,hwmods" property around for v5.2 kernel and only
drop it later on.

Note that there is no need to use property status = "disabled" for mmc3.
The default for dts is enabled, and runtime PM will idle unused instances
just fine.

Fixes: 4e27f752

 ("ARM: OMAP2+: Drop mmc platform data for am330x and am43xx")
Reported-by: David Lechner <david@lechnology.com>
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>