ARM: dts: DRA74x: Add aliases for rproc nodes

Add aliases for all the IPU and DSP remoteproc processor
nodes common to all DRA74x/DRA76x/AM572x/AM574x boards.
The aliases uses the stem "rproc". The aliases are defined
in the order of the most common processors on the DRA74x
family.

The aliases can be overridden, if needed, in the respective
derivative board dts files.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>