qcacmn: Revise to include walt.h header

Since walt is msm-only scheduler group of features,
not upstreamed. Include walt.h header when CONFIG_SCHED_WALT
has been enabled.

CRs-Fixed: 3023820
Change-Id: Ib1aacae83ca4168eff958341f0feebe8ab37a4e7

qdf/linux/src/qdf_threads.c

@@ -31,7 +31,9 @@
 #else
 #include <linux/sched/signal.h>
 #endif /* KERNEL_VERSION(4, 11, 0) */
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
+/* Test against msm kernel version */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)) && \
+	IS_ENABLED(CONFIG_SCHED_WALT)
 #include <linux/sched/walt.h>
 #endif
 #include <linux/delay.h>