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/hexagon/cpu_loop.c

@@ -55,7 +55,7 @@ void cpu_loop(CPUHexagonState *env)
                              env->gpr[4],
                              env->gpr[5],
                              0, 0);
-            if (ret == -TARGET_ERESTARTSYS) {
+            if (ret == -QEMU_ERESTARTSYS) {
                 env->gpr[HEX_REG_PC] -= 4;
             } else if (ret != -TARGET_QEMU_ESIGRETURN) {
                 env->gpr[0] = ret;