powerpc64/ftrace: Implement support for ftrace_regs_caller()

With -mprofile-kernel, we always save the full register state in
ftrace_caller(). While this works, this is inefficient if we're not
interested in the register state, such as when we're using the function
tracer.

Rename the existing ftrace_caller() as ftrace_regs_caller() and provide
a simpler implementation for ftrace_caller() that is used when registers
are not required to be saved.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/module.h

@@ -53,6 +53,9 @@ struct mod_arch_specific {
 #ifdef CONFIG_DYNAMIC_FTRACE
 	unsigned long toc;
 	unsigned long tramp;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+	unsigned long tramp_regs;
+#endif
 #endif
 
 	/* For module function descriptor dereference */