fs/buffer: add folio_create_empty_buffers helper

Folio version of create_empty_buffers().  This is required to convert
create_page_buffers() to folio_create_buffers() later in the series.

It removes several calls to compound_head() as it works directly on folio
compared to create_empty_buffers().  Hence, create_empty_buffers() has
been modified to call folio_create_empty_buffers().

Link: https://lkml.kernel.org/r/20230417123618.22094-4-p.raghav@samsung.com


Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>