osdep.h: For Haiku, define SIGIO as equivalent to SIGPOLL

Haiku doesn't provide SIGIO; fix this up in osdep.h by defining it as
equal to SIGPOLL.
Signed-off-by: NDavid Carlier <devnexen@gmail.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 20200703145614.16684-6-peter.maydell@linaro.org
[PMM: Expanded commit message]
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

include/qemu/osdep.h

@@ -432,6 +432,10 @@ void qemu_anon_ram_free(void *ptr, size_t size);
 #define HAVE_CHARDEV_PARPORT 1
 #endif
 
+#if defined(__HAIKU__)
+#define SIGIO SIGPOLL
+#endif
+
 #if defined(CONFIG_LINUX)
 #ifndef BUS_MCEERR_AR
 #define BUS_MCEERR_AR 4