linux-user: Rename TARGET_ERESTARTSYS to QEMU_ERESTARTSYS

This value is fully internal to qemu, and so is not a TARGET define.
We use this as an extra marker for both host and target errno.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/alpha/cpu_loop.c

@@ -98,7 +98,7 @@ void cpu_loop(CPUAlphaState *env)
                                     env->ir[IR_A2], env->ir[IR_A3],
                                     env->ir[IR_A4], env->ir[IR_A5],
                                     0, 0);
-                if (sysret == -TARGET_ERESTARTSYS) {
+                if (sysret == -QEMU_ERESTARTSYS) {
                     env->pc -= 4;
                     break;
                 }