hw/riscv/virt.c: enforce s->memmap use in machine_init()

hw/riscv/virt.c: enforce s->memmap use in machine_init()

Throughout the code we're accessing the board memmap, most of the time,
by accessing it statically via 'virt_memmap'. This static map is also
assigned in the machine state in s->memmap.

We're also passing it as a variable to some fdt functions, which is
unorthodox since we can spare a function argument by accessing it
statically or via the machine state.

All the current forms are valid but not all of the are scalable. In the
future we will version this board, and then all this code will need
rework because it should point to the updated memmap. In this case,
we'll want to assign the adequate versioned memmap once during init,
in s->memmap like it is being done today, and the rest of the code
will access the updated map via s->memmap.

We're also enforcing the pattern of using s->memmap instead of assigning
it to a temp variable 'memmap'. Code is copy/pasted around all the time
and being consistent is important.

We'll start these rather mechanical changes with virt_machine_init().

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Message-ID: <20250429125811.224803-2-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>