hw/omap_gpmc: Fix region map/unmap when configuring prefetch engine
When configuring the prefetch engine (and also when resetting from
a state where the prefetch engine was enabled) be careful to adhere
to the "unmap/change config fields/map" ordering, to avoid trying
to delete the wrong MemoryRegions. This fixes an assertion failure
in some cases.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reported-by: Alexander Graf <agraf@suse.de> Tested-by: Alexander Graf <agraf@suse.de>