video: fbdev: aty: radeon_pm: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>

drivers/video/fbdev/aty/radeon_pm.c

···
 	case 1:
 		if (mc & 0x4)
 			break;
+		/* fall through */
 	case 2:
 		dll_sleep_mask |= MDLL_R300_RDCK__MRDCKB_SLEEP;
 		dll_reset_mask |= MDLL_R300_RDCK__MRDCKB_RESET;
+		/* fall through */
 	case 0:
 		dll_sleep_mask |= MDLL_R300_RDCK__MRDCKA_SLEEP;
 		dll_reset_mask |= MDLL_R300_RDCK__MRDCKA_RESET;
···
 	case 1:
 		if (!(mc & 0x4))
 			break;
+		/* fall through */
 	case 2:
 		dll_sleep_mask |= MDLL_R300_RDCK__MRDCKD_SLEEP;
 		dll_reset_mask |= MDLL_R300_RDCK__MRDCKD_RESET;