- The comment is incorrectly indented / formatted.

- The comment states a 8MB limit, even though the code enforces a 16MB
  limit.

Both of these warts come from commit 0657c657 ("hw/i386/pc: add max
combined fw size as machine configuration option", 2020-12-09); clean them
up.

Arguably, it's also better to be consistent with the binary units (such as
"MiB") that QEMU uses nowadays.

Cc: "Michael S. Tsirkin" <mst@redhat.com> (supporter:PC)
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com> (supporter:PC)
Cc: Paolo Bonzini <pbonzini@redhat.com> (maintainer:X86 TCG CPUs)
Cc: Richard Henderson <richard.henderson@linaro.org> (maintainer:X86 TCG CPUs)
Cc: Eduardo Habkost <eduardo@habkost.net> (maintainer:X86 TCG CPUs)
Cc: qemu-trivial@nongnu.org
Fixes: 0657c657
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>