powerpc: Disable HCALL_STATS by default

The overhead of HCALL_STATS is quite high and the functionality is very
rarely used.  Key statistics are also missing (eg min/max).

With the new hcall tracepoints much more powerful tracing can be done in
a kernel module.  Lets disable this by default.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/configs/pseries_defconfig

@@ -1683,7 +1683,7 @@ CONFIG_HAVE_ARCH_KGDB=y
 CONFIG_DEBUG_STACKOVERFLOW=y
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_DEBUG_PAGEALLOC is not set
-CONFIG_HCALL_STATS=y
+# CONFIG_HCALL_STATS is not set
 # CONFIG_CODE_PATCHING_SELFTEST is not set
 # CONFIG_FTR_FIXUP_SELFTEST is not set
 # CONFIG_MSI_BITMAP_SELFTEST is not set