In the realize method of the msf2-soc SoC object, we call g_new() to
create new MemoryRegion objects for the nvm, nvm_alias, and sram.
This is unnecessary; make these MemoryRegions member fields of the
device state struct instead.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alexandre Iooss <erdnaxe@crans.org>
Message-id: 20210812093356.1946-19-peter.maydell@linaro.org