[SSB] Initialise dma_mask for SSB_BUSTYPE_SSB devices

For SSB_BUSTYPE_SSB type devices, we need to initialize dma_mask using
coherent_dma_mask so that calls to dma_set_mask() succeed.

It fixes the regression on the b44 driver introduced by commit
f225763a7d6c92c4932dbd528437997078496fcc

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

drivers/ssb/main.c

@@ -471,6 +471,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
 #endif
 			break;
 		case SSB_BUSTYPE_SSB:
+			dev->dma_mask = &dev->coherent_dma_mask;
 			break;
 		}