Update USDT argument constraint for powerpc and powerpc64

This updates the USDT argument constraint for powerpc and
powerpc64 from 'nQr' to 'nZr'. The 'Q' memory constraint
will allow a memory operand only if it is an offset from
a register. The 'Z' memory constraint is similar but will
additionally allow a memory operand that is an indexed or
indirect from a register. This offers more flexibility.
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>

tests/python/include/folly/tracing/StaticTracepoint-ELF.h

@@ -19,7 +19,7 @@
 // Default constraint for the probe arguments as operands.
 #ifndef FOLLY_SDT_ARG_CONSTRAINT
 #if defined(__powerpc64__) || defined(__powerpc__)
-#define FOLLY_SDT_ARG_CONSTRAINT      "nQr"
+#define FOLLY_SDT_ARG_CONSTRAINT      "nZr"
 #else
 #define FOLLY_SDT_ARG_CONSTRAINT      "nor"
 #endif