scsi: lpfc: Resolve checker warning for lpfc_new_io_buf()

Per Dan Carpenter:

The patch d79c9e9d4b3d: "scsi: lpfc: Support dynamic unbounded SGL lists on
G7 hardware." from Aug 14, 2019, leads to the following static checker
warning:

   drivers/scsi/lpfc/lpfc_init.c:4107 lpfc_new_io_buf()
  error: not allocating enough data 784 vs 768

There was no need to compare sizes nor to allocate size based on a define.

Change allocation to use actual structure length

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_init.c

@@ -4093,18 +4093,9 @@ lpfc_new_io_buf(struct lpfc_hba *phba, int num_to_alloc)
 	LIST_HEAD(post_nblist);
 	LIST_HEAD(nvme_nblist);
 
-	/* Sanity check to ensure our sizing is right for both SCSI and NVME */
-	if (sizeof(struct lpfc_io_buf) > LPFC_COMMON_IO_BUF_SZ) {
-		lpfc_printf_log(phba, KERN_ERR, LOG_FCP,
-				"6426 Common buffer size %zd exceeds %d\n",
-				sizeof(struct lpfc_io_buf),
-				LPFC_COMMON_IO_BUF_SZ);
-		return 0;
-	}
-
 	phba->sli4_hba.io_xri_cnt = 0;
 	for (bcnt = 0; bcnt < num_to_alloc; bcnt++) {
-		lpfc_ncmd = kzalloc(LPFC_COMMON_IO_BUF_SZ, GFP_KERNEL);
+		lpfc_ncmd = kzalloc(sizeof(*lpfc_ncmd), GFP_KERNEL);
 		if (!lpfc_ncmd)
 			break;
 		/*

drivers/scsi/lpfc/lpfc_sli4.h

@@ -44,9 +44,6 @@
 #define LPFC_HBA_HDWQ_MAX	128
 #define LPFC_HBA_HDWQ_DEF	0
 
-/* Common buffer size to accomidate SCSI and NVME IO buffers */
-#define LPFC_COMMON_IO_BUF_SZ	768
-
 /*
  * Provide the default FCF Record attributes used by the driver
  * when nonFIP mode is configured and there is no other default