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: Icd65573b02d95198e26c37ebe4ac93839cf21ad9
CRs-Fixed: 3553530

icnss2/main.c

@@ -4621,7 +4621,7 @@ 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);