powerpc/ftrace: Inline ftrace_modify_code()

Inlining ftrace_modify_code(), it increases a bit the
size of ftrace code but brings 5% improvment on ftrace
activation.

Usually in C files we let gcc decide what to do but here
it really help to 'help' gcc to decide to inline, thought
we don't want to force it with an __always_inline that
would be too much for CONFIG_CC_OPTIMIZE_FOR_SIZE.

Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/1597a06d[e-mail]

arch/powerpc/kernel/trace/ftrace.c

···
 	return op;
 }
 
-static int
+static inline int
 ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
 {
 	ppc_inst_t replaced;