blackfin: bf537: fix typo "CONFIG_SND_SOC_ADV80X_MODULE"

There's a (rather subtle) typo in "CONFIG_SND_SOC_ADV80X_MODULE". Fix it
once and for all by using IS_ENABLED(), which is designed to avoid
issues like this.

Signed-off-by: Paul Bolle <[e-mail]>

arch/blackfin/mach-bf537/boards/stamp.c

···
 	},
 #endif
 
-#if defined(CONFIG_SND_SOC_ADAV80X) || defined(CONFIG_SND_SOC_ADV80X_MODULE)
+#if IS_ENABLED(CONFIG_SND_SOC_ADAV80X)
 	{
 		.modalias = "adav801",
 		.max_speed_hz = 3125000,     /* max spi clock (SCK) speed in HZ */