linux-user: Fix stat64 syscall for SPARC64

linux-user: Fix stat64 syscall for SPARC64

Some targets use a stat64 structure for the stat64 syscall while others
use a stat structure. SPARC64 used the wrong kind.

Instead of extending the conditional compilation in syscall.c, now a
macro TARGET_HAS_STRUCT_STAT64 is defined whenever a target has a
target_stat64.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Erik de Castro Lopo <erikd@mega-nerd.com>
(cherry picked from commit 20d155bc902f41c5b354937e730ad85b43614ae9)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>