The qemu_mprotect_*() family of functions are used in very few files;
move them from osdep.h to a new qemu/mprotect.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220208200856.3558249-3-peter.maydell@linaro.org