powerpc/32s: Remove TAUException wart in traps.c

All 32 and 64-bit builds that don't have CONFIG_TAU_INT enabled (all
of them), get a definition of TAUException() in traps.c.

On 64-bit it's completely useless, and just wastes ~120 bytes of text.
On 32-bit it allows the kernel to link because head_32.S calls it
unconditionally.

Instead follow the example of altivec_assist_exception(), and if
CONFIG_TAU_INT is not enabled just point it at unknown_exception using
the preprocessor.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200724131728.1643966-6-mpe@ellerman.id.au

arch/powerpc/kernel/head_32.S

@@ -671,6 +671,10 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 
 #ifndef CONFIG_ALTIVEC
 #define altivec_assist_exception	unknown_exception
+#endif
+
+#ifndef CONFIG_TAU_INT
+#define TAUException	unknown_exception
 #endif
 
 	EXCEPTION(0x1300, Trap_13, instruction_breakpoint_exception, EXC_XFER_STD)

arch/powerpc/kernel/traps.c

@@ -2060,14 +2060,6 @@ void DebugException(struct pt_regs *regs, unsigned long debug_status)
 NOKPROBE_SYMBOL(DebugException);
 #endif /* CONFIG_PPC_ADV_DEBUG_REGS */
 
-#if !defined(CONFIG_TAU_INT)
-void TAUException(struct pt_regs *regs)
-{
-	printk("TAU trap at PC: %lx, MSR: %lx, vector=%lx    %s\n",
-	       regs->nip, regs->msr, regs->trap, print_tainted());
-}
-#endif /* CONFIG_INT_TAU */
-
 #ifdef CONFIG_ALTIVEC
 void altivec_assist_exception(struct pt_regs *regs)
 {