irqchip/irq-imx-gpcv2: Silence "fall through" warning

The -Wimplicit-fallthrough option requires that the /* fall through */
comment is placed in the 'case' statement that falls through, rather
than in the following one. Case seems to matter as well.

Reported-by: Stephen Rothwell <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

drivers/irqchip/irq-imx-gpcv2.c

···
 		case 4:
 			writel_relaxed(~0, reg + GPC_IMR1_CORE2);
 			writel_relaxed(~0, reg + GPC_IMR1_CORE3);
-		case 2:	      /* FALLTHROUGH */
+			/* fall through */
+		case 2:
 			writel_relaxed(~0, reg + GPC_IMR1_CORE0);
 			writel_relaxed(~0, reg + GPC_IMR1_CORE1);
 		}