Don't spam the console with an additional, and useless, error message.

There's no need to spam the console with this error message. If there's an I/O
error, the disk/cam driver will report it at the lower levels. If that's an
actual problem, the upper layers will report that.

Reviewed by: kib@
Differential Revision:  https://reviews.freebsd.org/D23756

sys/vm/vnode_pager.c

@@ -1169,8 +1169,6 @@ vnode_pager_generic_getpages_done(struct buf *bp)
 			vm_page_readahead_finish(mt);
 	}
 	VM_OBJECT_RUNLOCK(object);
-	if (error != 0)
-		printf("%s: I/O read error %d\n", __func__, error);
 
 	return (error);
 }