rename CONFIG_EPOLL_CREATE1 to CONFIG_EPOLL, and stop checking for epoll in meson.build

Since CONFIG_EPOLL is now unused, it's okay to
perform this rename, to make it less ugly.

Since epoll is linux-specific and is always present on linux,
define CONFIG_EPOLL to 1 on linux, without compile-time test.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

meson.build

@@ -2685,8 +2685,7 @@ config_host_data.set('CONFIG_INOTIFY1', have_inotify_init1)
 # has_header_symbol
 config_host_data.set('CONFIG_BLKZONED',
                      cc.has_header_symbol('linux/blkzoned.h', 'BLKOPENZONE'))
-config_host_data.set('CONFIG_EPOLL_CREATE1',
-                     cc.has_header_symbol('sys/epoll.h', 'epoll_create1'))
+config_host_data.set('CONFIG_EPOLL', host_os == 'linux')
 config_host_data.set('CONFIG_FALLOCATE_PUNCH_HOLE',
                      cc.has_header_symbol('linux/falloc.h', 'FALLOC_FL_PUNCH_HOLE') and
                      cc.has_header_symbol('linux/falloc.h', 'FALLOC_FL_KEEP_SIZE'))

util/aio-posix.h

@@ -52,7 +52,7 @@ extern const FDMonOps fdmon_poll_ops;
 /* Switch back to poll(2). list_lock must be held. */
 void fdmon_poll_downgrade(AioContext *ctx);
 
-#ifdef CONFIG_EPOLL_CREATE1
+#ifdef CONFIG_EPOLL
 bool fdmon_epoll_try_upgrade(AioContext *ctx, unsigned npfd);
 void fdmon_epoll_setup(AioContext *ctx);
 
@@ -71,7 +71,7 @@ static inline void fdmon_epoll_setup(AioContext *ctx)
 static inline void fdmon_epoll_disable(AioContext *ctx)
 {
 }
-#endif /* !CONFIG_EPOLL_CREATE1 */
+#endif /* !CONFIG_EPOLL */
 
 #ifdef CONFIG_LINUX_IO_URING
 bool fdmon_io_uring_setup(AioContext *ctx, Error **errp);

util/meson.build

@@ -3,7 +3,7 @@ util_ss.add(files('thread-context.c'), numa)
 if host_os != 'windows'
   util_ss.add(files('aio-posix.c'))
   util_ss.add(files('fdmon-poll.c'))
-  if config_host_data.get('CONFIG_EPOLL_CREATE1')
+  if config_host_data.get('CONFIG_EPOLL')
     util_ss.add(files('fdmon-epoll.c'))
   endif
   util_ss.add(files('compatfd.c'))