RDMA/efa: Use offset_in_page() function

Use offset_in_page() instead of open-coding it.

Link: https://lore.kernel.org/r/20240624160918.27060-2-mrgolin@amazon.com
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Reviewed-by: Firas Jahjah <firasj@amazon.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Michael Margolin <mrgolin@amazon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/efa/efa_verbs.c

@@ -524,7 +524,7 @@ static int qp_mmap_entries_setup(struct efa_qp *qp,
 
 	address = dev->mem_bar_addr + resp->llq_desc_offset;
 	length = PAGE_ALIGN(params->sq_ring_size_in_bytes +
-			    (resp->llq_desc_offset & ~PAGE_MASK));
+			    offset_in_page(resp->llq_desc_offset));
 
 	qp->llq_desc_mmap_entry =
 		efa_user_mmap_entry_insert(&ucontext->ibucontext,