kernel: kcov: include missing header for ‘struct task_struct’

Include linux/sched.h to fix "dereferencing pointer to incomplete type
‘struct task_struct’" build error for ARCH=x86_64.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
diff --git a/kernel/kcov.c b/kernel/kcov.c
index 3efbee0..e228cb1 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -12,6 +12,7 @@
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/kcov.h>
+#include <linux/sched.h>
 
 /*
  * kcov descriptor (one per opened debugfs file).