MIPS: Setup errno for {f,l,}xstat

{f,l,}xstat stub for MIPS is using INTERNAL_SYSCALL
to do xstat syscall for glibc ver, However it leaves
errno untouched and thus giving bad errno output.

Setup errno properly when syscall returns non-zero.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

(cherry picked from commit 66016ec8)