asm-generic: unistd.h: fixup broken macro include.

asm-generic: unistd.h: fixup broken macro include.

The broken macros make the glibc compile error. If there is no
__NR3264_fstat*, we should also removed related definitions.

Reported-by: Marcin Juszkiewicz <[email protected]>
Fixes: bf4b6a7d371e ("y2038: Remove stat64 family from default syscall set")
[arnd: Both Marcin and Guo provided this patch to fix up my clearly
       broken commit, I applied the version with the better changelog.]
Signed-off-by: Guo Ren <[email protected]>
Signed-off-by: Mao Han <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>