microblaze: ftrace: Pass the first calling instruction for dynamic ftrace

Selftest for dynamic ftrace requres to pass address of the first
calling instruction because hash function is calculated from it.

ftrace_update_ftrace_func setups pointer to function which is called
in _mcount function. trace_selftest is not aware about instruction
size (for microblaze 8 - imm and addik) and that's why we have
to pass in r5 address of imm not addik which is in r15.12

For more info look at ftrace_ops_list_func/ftrace.c.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/mcount.S

@@ -138,7 +138,7 @@ NOALIGN_ENTRY(ftrace_call)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 /* static normal trace */
 	lwi	r6, r1, 120; /* MS: load parent addr */
-	addik	r5, r15, 0; /* MS: load current function addr */
+	addik	r5, r15, -4; /* MS: load current function addr */
 	/* MS: here is dependency on previous code */
 	brald	r15, r20; /* MS: jump to ftrace handler */
 	nop;