ext4: rename ext4_xattr_check_names() to ext4_xattr_check_entries()

ext4_xattr_check_names() actually validates both the xattr names and
values, not just the names.  So rename it to ext4_xattr_check_entries()
to avoid confusion.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>