jbd2: use a folio in jbd2_journal_write_metadata_buffer()

jbd2: use a folio in jbd2_journal_write_metadata_buffer()

The primary goal here is removing the use of set_bh_page().  Take the
opportunity to switch from kmap_atomic() to kmap_local().  This simplifies
the function as the offset is already added to the pointer.

Link: https://lkml.kernel.org/r/20230713035512.4139457-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Cc: Tom Rix <trix@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>