cnss2: Correctly check for WCNSS_MEM_PRE_ALLOC macro

After CNSS2 switched to Bazel based compilation, conditional
compilation macros became same as configs and are enabled
directly from defconfig. Fix macro check in the code for
both 'y' or 'm' to enable code based on the that.

Change-Id: I12ca87c851a7b47af0255716ce1b9f59ad2eb70a
CRs-Fixed: 3553530

icnss2/main.c

@@ -4620,7 +4620,7 @@ static void rproc_restart_level_notifier(void *data, struct rproc *rproc)
 	}
 }
 
-#ifdef CONFIG_WCNSS_MEM_PRE_ALLOC
+#if IS_ENABLED(CONFIG_WCNSS_MEM_PRE_ALLOC)
 static void icnss_initialize_mem_pool(unsigned long device_id)
 {
 	cnss_initialize_prealloc_pool(device_id);