tools/lib/: split non-SPI code from atusb.c in preparation for SPI-based driver

- atusb.c (atusb_error, atusb_clear_error, atusb_open, atusb_close,
  atusb_reset, atusb_reset_rf, atusb_test_mode, atusb_slp_tr,
  atusb_interrupt, atusb_set_clkm, atusb_dev_handle): moved to
  atusb-common.c
- atusb-common.c (atusb_set_clkm): pass atusb_reg_write via
  atusb_driver.reg_write instead
- atusb.c (FROM_DEV, TO_DEV, struct atusb_dsc): moved to atusb-common.h
- Makefile (OBJS): added atusb-common.o

tools/lib/atusb-common.h

@@ -0,0 +1,39 @@
+/*
+ * lib/atusb-common.h - ATUSB access functions shared by all ATUSB drivers
+ *
+ * Written 2010-2011 by Werner Almesberger
+ * Copyright 2010-2011 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#ifndef ATUSB_COMMON_H
+#define	ATUSB_COMMON_H
+
+
+#define FROM_DEV        ATUSB_FROM_DEV(0)
+#define TO_DEV          ATUSB_TO_DEV(0)
+
+
+struct atusb_dsc {
+	usb_dev_handle *dev;
+	int error;
+};
+
+
+int atusb_error(void *handle);
+int atusb_clear_error(void *handle);
+void *atusb_open(const char *arg);
+void atusb_close(void *handle);
+void atusb_reset(void *handle);
+void atusb_reset_rf(void *handle);
+void atusb_test_mode(void *handle);
+void atusb_slp_tr(void *handle, int on, int pulse);
+int atusb_interrupt(void *handle);
+int atusb_set_clkm(void *handle, int mhz);
+
+#endif /* !ATUSB_COMMON_H */