smb: do not test the return value of folio_start_writeback()

smb: do not test the return value of folio_start_writeback()

[ Upstream commit a9540e35624d1475f47dbf6353eed8b99936d36e ]

In preparation for removing the return value entirely, stop testing it
in smb.

Link: https://lkml.kernel.org/r/20231108204605.745109-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: f3dc1bdb6b0b ("cifs: Fix writeback data corruption")
Signed-off-by: Sasha Levin <sashal@kernel.org>