linux-user/xtensa: remove stray syscall.h

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
diff --git a/linux-user/xtensa/syscall.h b/linux-user/xtensa/syscall.h
deleted file mode 100644
index e69de29..0000000
--- a/linux-user/xtensa/syscall.h
+++ /dev/null