target-sparc: fix Trap Based Address Register behavior for sparc64

Accoding the chapter 7.6 Trap Processing of the SPARC Architecture Manual v9,
the Trap Based Address Register is not modified as a trap is taken.

This fix allows booting FreeBSD-10.3-RELEASE-sparc64.
Signed-off-by: NArtyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

target-sparc/int64_helper.c

@@ -158,9 +158,8 @@ void sparc_cpu_do_interrupt(CPUState *cs)
     } else if ((intno & 0x1c0) == TT_FILL) {
         cpu_set_cwp(env, cpu_cwp_inc(env, env->cwp + 1));
     }
-    env->tbr &= ~0x7fffULL;
-    env->tbr |= ((env->tl > 1) ? 1 << 14 : 0) | (intno << 5);
-    env->pc = env->tbr;
+    env->pc = env->tbr  & ~0x7fffULL;
+    env->pc |= ((env->tl > 1) ? 1 << 14 : 0) | (intno << 5);
     env->npc = env->pc + 4;
     cs->exception_index = -1;
 }