hw/i386/x86: Eliminate two if statements in x86_bios_rom_init()

hw/i386/x86: Eliminate two if statements in x86_bios_rom_init()

Given that memory_region_set_readonly() is a no-op when the readonlyness is
already as requested it is possible to simplify the pattern

  if (condition) {
    foo(true);
  }

to

  foo(condition);

which is shorter and allows to see the invariant of the code more easily.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240430150643.111976-2-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>