eventfs: Implement eventfs lookup, read, open functions

eventfs: Implement eventfs lookup, read, open functions

Add the inode_operations, file_operations, and helper functions to eventfs:
dcache_dir_open_wrapper()
eventfs_root_lookup()
eventfs_release()
eventfs_set_ef_status_free()
eventfs_post_create_dir()

The inode_operations and file_operations functions will be called from the
VFS layer.

create_file() and create_dir() are added as stub functions and will be
filled in later.

Link: https://lkml.kernel.org/r/1690568452-46553-7-git-send-email-akaher@vmware.com
Signed-off-by: Ajay Kaher <akaher@vmware.com>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: Ching-lin Yu <chinglinyu@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>