powerpc/perf: Drop the case of returning 0 as instruction pointer

Drop the case of returning 0 as instruction pointer since kernel
never executes at 0 and userspace almost never does either.

Fixes: e6878835 ("powerpc/perf: Sample only if SIAR-Valid bit is set in P7+")
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210818171556.36912-2-kjain@linux.ibm.com

arch/powerpc/perf/core-book3s.c

@@ -2270,8 +2270,6 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)
 			return regs->nip;
 	} else if (use_siar && siar_valid(regs))
 		return siar + perf_ip_adjust(regs);
-	else if (use_siar)
-		return 0;		// no valid instruction pointer
 	else
 		return regs->nip;
 }