powerpc: use __kernel_{uid,gid}32_t in uapi/asm/stat.h

Commit c01013a2 ("powerpc: add asm/stat.h to UAPI compile-test
coverage") converted as follows:

  uid_t  -->  __kernel_uid_t
  gid_t  -->  __kernel_gid_t

The bit width of __kernel_{uid,gid}_t is 16 or 32-bits depending on
architectures.

PPC uses 32-bits for them as in include/uapi/asm-generic/posix_types.h,
so the previous conversion is probably fine, but let's stick to the
arch-independent conversion just in case.

The safe replacements across all architectures are:

  uid_t  -->  __kernel_uid32_t
  gid_t  -->  __kernel_gid32_t

as defined in include/linux/types.h.

A similar issue was reported for the android binder. [1]

[1]: https://lore.kernel.org/all/20220601010017.2639048-1-cmllamas@google.com/

Fixes: c01013a2 ("powerpc: add asm/stat.h to UAPI compile-test coverage")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/powerpc/include/uapi/asm/stat.h

@@ -37,8 +37,8 @@ struct stat {
 	__kernel_mode_t	st_mode;
 	unsigned short	st_nlink;
 #endif
-	__kernel_uid_t	st_uid;
-	__kernel_gid_t	st_gid;
+	__kernel_uid32_t st_uid;
+	__kernel_gid32_t st_gid;
 	unsigned long	st_rdev;
 	long		st_size;
 	unsigned long	st_blksize;