Update Linux to v5.4.148

Sourced from [1]

[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.148.tar.gz

Change-Id: Ib3d26c5ba9b022e2e03533005c4fed4d7c30b61b
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 1bb85f6..7df6b26 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -57,6 +57,7 @@
  * >	brasl	%r0,ftrace_caller	# offset 0
  */
 
+void *ftrace_func __read_mostly = ftrace_stub;
 unsigned long ftrace_plt;
 
 static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
@@ -166,6 +167,7 @@
 
 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
+	ftrace_func = func;
 	return 0;
 }