mips: fixup blksys_restart address for mips64

Restart logic has changed in kernel, this is counterpart in Valgrind.

This change fixes:

none/tests/syscall-restart1
none/tests/syscall-restart2

for mips64.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13379

coregrind/m_syswrap/syscall-mips64-linux.S

@@ -100,9 +100,8 @@ ML_(do_syscall_for_client_WRK):
 
    ld      $5, OFFSET_mips64_r5($5)  /* a1 */
    ld      $2, 0($29)                /* syscallno */
-2: nop
 
-   syscall
+2: syscall
 
    /* Saving return values into Guest state  */
 3: ld      $5, 8($29)                /* guest_state */