Simple change to fix building in recent environments

Renamed _fini too for symmetry.

Suggested-by: @ensch
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #12059
Closes: #11987
Closes: #12056

module/os/linux/zfs/zfs_ioctl_os.c

@@ -277,7 +277,7 @@ zfsdev_detach(void)
 #endif
 
 static int __init
-_init(void)
+openzfs_init(void)
 {
 	int error;
 
@@ -303,7 +303,7 @@ _init(void)
 }
 
 static void __exit
-_fini(void)
+openzfs_fini(void)
 {
 	zfs_sysfs_fini();
 	zfs_kmod_fini();
@@ -313,8 +313,8 @@ _fini(void)
 }
 
 #if defined(_KERNEL)
-module_init(_init);
-module_exit(_fini);
+module_init(openzfs_init);
+module_exit(openzfs_fini);
 #endif
 
 ZFS_MODULE_DESCRIPTION("ZFS");