sparc32: Fix struct stat uid/gid types.

Commit 085219f7
("sparc32: use proper types in struct stat")

Accidently changed the struct stat uid/gid members
to uid_t and gid_t, but those get set to
__kernel_uid32_t and __kernel_gid32_t respectively.
Those are of type 'int' but the structure is meant
to have 'short'.  So use uid16_t and gid16_t to
correct this.

Reported-by: Rob Landley <rob@landley.net>
Signed-off-by: David S. Miller <davem@davemloft.net>