powerpc/syscalls: Fix syscall tracing

Recently in commit fbf508da ("powerpc: split compat syscall table
out from native table") we changed the layout of the system call
table. Instead of having two entries for each syscall number, one for
the regular entry point and one for the compat entry point, we now
have separate tables for regular and compat entry points.

This inadvertently broke syscall tracing (CONFIG_FTRACE_SYSCALLS),
because our implementation of arch_syscall_addr() knew about the
layout of the table (it did nr * 2).

We can fix it just by dropping our version of arch_syscall_addr() and
using the generic version which does:

	return (unsigned long)sys_call_table[nr];

Fixes: fbf508da ("powerpc: split compat syscall table out from native table")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/trace/ftrace.c

@@ -967,13 +967,6 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
-#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
-unsigned long __init arch_syscall_addr(int nr)
-{
-	return sys_call_table[nr*2];
-}
-#endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */
-
 #ifdef PPC64_ELF_ABI_v1
 char *arch_ftrace_match_adjust(char *str, const char *search)
 {