iomap: move the iomap_sector sector calculation out of iomap_add_to_ioend

iomap: move the iomap_sector sector calculation out of iomap_add_to_ioend

The calculation in iomap_sector is pretty trivial and most of the time
iomap_add_to_ioend only callers either iomap_can_add_to_ioend or
iomap_alloc_ioend from a single invocation.

Calculate the sector in the two lower level functions and stop passing it
from iomap_add_to_ioend and update the iomap_alloc_ioend argument passing
order to match that of iomap_add_to_ioend.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231207072710.176093-9-hch@lst.de
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>