hw/arm/stm32: Use memory_region_init_rom() with read-only regions
The scripts/coccinelle/memory-region-housekeeping.cocci reported:
* TODO [[view:./hw/arm/stm32f205_soc.c::face=ovl-face1::linb=96::colb=4::cole=26][potential use of memory_region_init_rom*() in ./hw/arm/stm32f205_soc.c::96]]
* TODO [[view:./hw/arm/stm32f405_soc.c::face=ovl-face1::linb=98::colb=4::cole=26][potential use of memory_region_init_rom*() in ./hw/arm/stm32f405_soc.c::98]]
We can indeed replace the memory_region_init_ram() and
memory_region_set_readonly() calls by memory_region_init_rom().
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>