linux-user: move uname functions to uname.c

Make syscall.c slightly smaller by moving uname-related
functions to uname.c.

Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

linux-user/uname.h

@@ -1 +1,10 @@
+#ifndef UNAME_H
+#define UNAME_H 1
+
+#include <sys/utsname.h>
+#include <linux/utsname.h>
+
 const char *cpu_to_uname_machine(void *cpu_env);
+int sys_uname(struct new_utsname *buf);
+
+#endif /* UNAME _H */