epoll.h: Add epoll ioctls

add two ioctls to get and set struct epoll_params to allow users to
control epoll based busy polling of network sockets.

added to uapi in commit 18e2bf0edf4dd88d9656ec92395aa47392e85b61 (Linux
kernel 6.9 and newer).

Signed-off-by: Joe Damato <jdamato@fastly.com>

libc/sysdeps/linux/common/sys/epoll.h

@@ -19,6 +19,7 @@
 #define	_SYS_EPOLL_H	1
 
 #include <stdint.h>
+#include <sys/ioctl.h>
 #include <sys/types.h>
 
 /* Get __sigset_t.  */
@@ -87,6 +88,19 @@ struct epoll_event
   epoll_data_t data;	/* User data variable */
 } __EPOLL_PACKED;
 
+struct epoll_params
+{
+  uint32_t busy_poll_usecs;
+  uint16_t busy_poll_budget;
+  uint8_t prefer_busy_poll;
+
+  /* pad the struct to a multiple of 64bits */
+  uint8_t __pad;
+};
+
+#define EPOLL_IOC_TYPE 0x8A
+#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
+#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
 
 __BEGIN_DECLS