stat64 wrong on sparc64 user

[Luca Bonissi]

On qemu-sparc64 (userspace) the struct "target_stat64" is not correctly 
padded, so the field st_rdev is not correctly aligned and will report 
wrong major/minor (e.g. for /dev/zero it reports 0,0x10500000 instead of 
1,5).

Here patch to solve the issue (it also fixes incorrect size on some fields):
--- qemu-20230327/linux-user/syscall_defs.h	2023-03-27 
15:41:42.000000000 +0200
+++ qemu-20230327/linux-user/syscall_defs.h.new	2023-03-27 
21:43:25.615115126 +0200
@@ -1450,7 +1450,7 @@ struct target_stat {
        unsigned int    st_dev;
        abi_ulong       st_ino;
        unsigned int    st_mode;
-       unsigned int    st_nlink;
+       short int       st_nlink;
        unsigned int    st_uid;
        unsigned int    st_gid;
        unsigned int    st_rdev;
@@ -1465,8 +1465,7 @@ struct target_stat {

 #define TARGET_HAS_STRUCT_STAT64
 struct target_stat64 {
-       unsigned char   __pad0[6];
-       unsigned short  st_dev;
+       uint64_t        st_dev;

        uint64_t        st_ino;
        uint64_t        st_nlink;
@@ -1476,14 +1475,13 @@ struct target_stat64 {
        unsigned int    st_uid;
        unsigned int    st_gid;

-       unsigned char   __pad2[6];
-       unsigned short  st_rdev;
+       unsigned int    __pad0;
+       uint64_t        st_rdev;

         int64_t                st_size;
        int64_t         st_blksize;

-       unsigned char   __pad4[4];
-       unsigned int    st_blocks;
+       int64_t         st_blocks;

        abi_ulong       target_st_atime;
        abi_ulong       target_st_atime_nsec;
@@ -1522,8 +1520,7 @@ struct target_stat {

 #define TARGET_HAS_STRUCT_STAT64
 struct target_stat64 {
-       unsigned char   __pad0[6];
-       unsigned short  st_dev;
+       uint64_t st_dev;

        uint64_t st_ino;

@@ -1533,8 +1530,7 @@ struct target_stat64 {
        unsigned int    st_uid;
        unsigned int    st_gid;

-       unsigned char   __pad2[6];
-       unsigned short  st_rdev;
+       uint64_t        st_rdev;

        unsigned char   __pad3[8];