ASoC: Intel: Atom: remove useless assignment

Fix cppcheck warning:

sound/soc/intel/atom/sst/sst.c:52:20: style: Variable 'size' is
assigned a value that is never used. [unreadVariable]
 unsigned int size = 0;
                   ^
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200813200147.61990-9-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst/sst.c

@@ -49,7 +49,7 @@ static irqreturn_t intel_sst_interrupt_mrfld(int irq, void *context)
 	union ipc_header_mrfld header;
 	union sst_imr_reg_mrfld imr;
 	struct ipc_post *msg = NULL;
-	unsigned int size = 0;
+	unsigned int size;
 	struct intel_sst_drv *drv = (struct intel_sst_drv *) context;
 	irqreturn_t retval = IRQ_HANDLED;