MDEV-8684: Use POWER wrappers rather than direct asm

i.e. __ppc_set_ppr_low rather than 'or 1,1,1'

configure.cmake

@@ -857,10 +857,11 @@ IF(NOT CMAKE_CROSSCOMPILING AND NOT MSVC)
   ENDIF()
   IF (NOT HAVE_PAUSE_INSTRUCTION)
     CHECK_C_SOURCE_COMPILES("
+    #include <sys/platform/ppc.h>
     int main()
     {
-     __asm__ __volatile__ (\"or 1,1,1\");
-     __asm__ __volatile__ (\"or 2,2,2\");
+     __ppc_set_ppr_low();
+     __ppc_set_ppr_med();
      return 0;
     }
     " HAVE_HMT_PRIORITY_INSTRUCTION)

storage/innobase/include/ut0ut.h

@@ -100,8 +100,9 @@ struct ut_when_dtor {
 #define UT_COMPILER_BARRIER() __asm__ __volatile__ ("":::"memory")
 
 # if defined(HAVE_HMT_PRIORITY_INSTRUCTION)
-#  define UT_LOW_PRIORITY_CPU() __asm__ __volatile__ ("or 1,1,1")
-#  define UT_RESUME_PRIORITY_CPU() __asm__ __volatile__ ("or 2,2,2")
+#include <sys/platform/ppc.h>
+#  define UT_LOW_PRIORITY_CPU() __ppc_set_ppr_low()
+#  define UT_RESUME_PRIORITY_CPU() __ppc_set_ppr_med()
 # else
 #  define UT_LOW_PRIORITY_CPU() ((void)0)
 #  define UT_RESUME_PRIORITY_CPU() ((void)0)

storage/xtradb/include/ut0ut.h

@@ -97,8 +97,9 @@ struct ut_when_dtor {
 #define UT_COMPILER_BARRIER() __asm__ __volatile__ ("":::"memory")
 
 # if defined(HAVE_HMT_PRIORITY_INSTRUCTION)
-#  define UT_LOW_PRIORITY_CPU() __asm__ __volatile__ ("or 1,1,1")
-#  define UT_RESUME_PRIORITY_CPU() __asm__ __volatile__ ("or 2,2,2")
+#include <sys/platform/ppc.h>
+#  define UT_LOW_PRIORITY_CPU() __ppc_set_ppr_low()
+#  define UT_RESUME_PRIORITY_CPU() __ppc_set_ppr_med()
 # else
 #  define UT_LOW_PRIORITY_CPU() ((void)0)
 #  define UT_RESUME_PRIORITY_CPU() ((void)0)