cxl/pci: Remove outdated FIXME comment and BUILD_BUG_ON

Remove the outdated FIXME comment about switching to struct_group() and
the associated BUILD_BUG_ON check. This work was already completed in
commit 301e68d ("cxl/core: Replace unions with struct_group()")
which converted struct cxl_regs to use struct_group_tagged().

The BUILD_BUG_ON was checking that anonymous union layout was preserved,
but since struct_group() now handles this correctly, the compile-time
check is no longer necessary.

Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260105203833.1604585-1-samasth.norway.ananda@oracle.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: samasth-norway

drivers/cxl/pci.c

@@ -912,13 +912,6 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	unsigned int i;
 	bool irq_avail;
 
-	/*
-	 * Double check the anonymous union trickery in struct cxl_regs
-	 * FIXME switch to struct_group()
-	 */
-	BUILD_BUG_ON(offsetof(struct cxl_regs, memdev) !=
-		     offsetof(struct cxl_regs, device_regs.memdev));
-
 	rc = pcim_enable_device(pdev);
 	if (rc)
 		return rc;