iomap: iomap_write_failed fix

The @lend parameter of truncate_pagecache_range() should be the offset
of the last byte of the hole, not the first byte beyond it.

Fixes: ae259a9c ("fs: introduce iomap infrastructure")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>