drm: include <poll.h> instead of <sys/poll.h>

I'm not sure what systems have <sys/poll.h> (maybe there are historical
reasons why some would), but POSIX defines <poll.h>. Although this code
is full of highly OS specific calls (like ioctl()), there's no reason
not to use the more standard include path.

video/out/drm_common.c

@@ -19,7 +19,7 @@
 #include <string.h>
 #include <signal.h>
 #include <sys/ioctl.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <sys/stat.h>
 #include <sys/vt.h>
 #include <unistd.h>

video/out/opengl/context_drm_egl.c

@@ -20,7 +20,7 @@
 #include <fcntl.h>
 #include <signal.h>
 #include <string.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <time.h>
 #include <unistd.h>
 

video/out/vo_drm.c

@@ -20,7 +20,7 @@
 #include <fcntl.h>
 #include <stdbool.h>
 #include <sys/mman.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <unistd.h>
 
 #include <libswscale/swscale.h>