of: reserved_mem: rework fdt_init_reserved_mem_node()

of: reserved_mem: rework fdt_init_reserved_mem_node()

Move the content of fdt_reserved_mem_save_node() to
fdt_init_reserved_mem_node() function. Initialization is no longer
performed in two steps as it was initially, so
fdt_reserved_mem_save_node() name is a bit misleading and that function
now performs full initialization of the reserved memory region.

This also fixes the problem of keeping pointers to the regions, which
failed to initialize, what might cause issues when such region is
assigned to the device.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://patch.msgid.link/20260325090023.3175348-8-m.szyprowski@samsung.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>