powerpc/pseries: address checkpatch warnings in dlpar_offline_cpu

Remove some stray blank lines, convert a printk to pr_warn, and
address a line length violation.

One functional change: use WARN_ON instead of BUG_ON in case H_PROD of
a ceded thread yields an unexpected result from the platform. We can
expect this code path to get uninterruptibly stuck in __cpu_die() if
this happens, but that's more desirable than crashing.
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Fixes: b6db63d1 ("pseries/pseries: Add code to online/offline CPUs of a DLPAR node")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191016183611.10867-2-nathanl@linux.ibm.com

arch/powerpc/platforms/pseries/hotplug-cpu.c

@@ -539,7 +539,6 @@ static int dlpar_offline_cpu(struct device_node *dn)
 					goto out;
 				cpu_maps_update_begin();
 				break;
-
 			}
 
 			/*
@@ -547,19 +546,19 @@ static int dlpar_offline_cpu(struct device_node *dn)
 			 * Upgrade it's state to CPU_STATE_OFFLINE.
 			 */
 			set_preferred_offline_state(cpu, CPU_STATE_OFFLINE);
-			BUG_ON(plpar_hcall_norets(H_PROD, thread)
-								!= H_SUCCESS);
+			WARN_ON(plpar_hcall_norets(H_PROD, thread) != H_SUCCESS);
 			__cpu_die(cpu);
 			break;
 		}
-		if (cpu == num_possible_cpus())
-			printk(KERN_WARNING "Could not find cpu to offline with physical id 0x%x\n", thread);
+		if (cpu == num_possible_cpus()) {
+			pr_warn("Could not find cpu to offline with physical id 0x%x\n",
+				thread);
+		}
 	}
 	cpu_maps_update_done();
 
 out:
 	return rc;
-
 }
 
 static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)