Use unprivileged read from %tick register to avoid SIGILL on sparc64.

Index: library/timing.c
--- library/timing.c.orig
+++ library/timing.c
@@ -137,7 +137,7 @@ unsigned long mbedtls_timing_hardclock( void )
 #if !defined(HAVE_HARDCLOCK) && defined(MBEDTLS_HAVE_ASM) &&  \
     defined(__GNUC__) && defined(__sparc64__)
 
-#if defined(__OpenBSD__)
+#if 0
 #warning OpenBSD does not allow access to tick register using software version instead
 #else
 #define HAVE_HARDCLOCK
@@ -145,7 +145,7 @@ unsigned long mbedtls_timing_hardclock( void )
 unsigned long mbedtls_timing_hardclock( void )
 {
     unsigned long tick;
-    asm volatile( "rdpr %%tick, %0;" : "=&r" (tick) );
+    asm volatile( "rd %%tick, %0;" : "=&r" (tick) );
     return( tick );
 }
 #endif /* __OpenBSD__ */