powerpc: Disable mcount tracers in pseries defconfig

IRQSOFF_TRACER and STACK_TRACER force the kernel to be built with -pg
which is a substantial overhead.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/configs/pseries_defconfig

@@ -311,9 +311,7 @@ CONFIG_DEBUG_KERNEL=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
 CONFIG_LATENCYTOP=y
 CONFIG_SYSCTL_SYSCALL_CHECK=y
-CONFIG_IRQSOFF_TRACER=y
 CONFIG_SCHED_TRACER=y
-CONFIG_STACK_TRACER=y
 CONFIG_BLK_DEV_IO_TRACE=y
 CONFIG_DEBUG_STACKOVERFLOW=y
 CONFIG_DEBUG_STACK_USAGE=y