remoteproc: k3: Refactor reserved_mem_init() functions into common driver

remoteproc: k3: Refactor reserved_mem_init() functions into common driver

The reserved_mem_init() implementations in the R5, DSP and M4 remoteproc
drivers initialize the reserved memory regions associated with the
remote processor.

Refactor these functions into the ti_k3_common.c driver as
k3_reserved_mem_init() and use this common function throughout in R5,
DSP and M4 drivers.

Signed-off-by: Beleswar Padhi <b-padhi@ti.com>
Tested-by: Judith Mendez <jm@ti.com>
Reviewed-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20250513054510.3439842-36-b-padhi@ti.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>