Merged uSD driver into unified tool build, completed conversion of tools.

- atusd/tools/lib/atusd.c: moved to tools/lib/
- atusd/tools/lib/atusd.h: removed, we can now use tools/include/atspi.h
- tools/lib/atusd.c: added copyright header
- tools/lib/atusd.c: updated for driver API
- tools/lib/Makefile: added atusd.o
- tools/Makefile.common: moved common elements from all other makefiles in
  tools/*/ here
- tools/Makefile.common: added target-specific compiler and flags
- tools/atspi-id/Makefile, tools/atspi-reset/Makefile,
  tools/atspi-rssi/Makefile, tools/atspi-trim/Makefile,
  tools/atspi-txrx/Makefile, tools/lib/Makefile: used Makefile.common
- tools/lib/Makefile: differentiate USB and uSD build
- tools/atspi-id/atspi-id.c, tools/atspi-reset/atspi-reset.c,
  tools/atspi-rssi/atspi-rssi.c, tools/atspi-trim/atspi-trim.c,
  tools/atspi-txr/atspi-txr.c: updated for driver-agnostic API
- tools/atspi-id/atspi-id.c, tools/atspi-reset/atspi-reset.c,
  tools/atspi-rssi/atspi-rssi.c, tools/atspi-trim/atspi-trim.c,
  tools/atspi-txr/atspi-txr.c: corrected AF86RF230 typo in title
- tools/include/atspi.h, tools/lib/atspi.c, tools/lib/driver.c,
  tools/lib/atusb.c: brought back support for atspi_error and
  atspi_clear_error
- tools/atspi-id/atspi-id.c (atspi_get_protocol): renamed to get_protocol,
  to make it clear that it's not from libatspi
- tools/atspi-id/atspi-id.c (atspi_get_build): renamed to get_build, to
  make it clear that it's not from libatspi
- tools/include/atspi.h, tools/lib/atspi.c (atspi_usb_handle): new function
  to obtain a driver's USB device handle (or NULL if the driver doesn't use
  USB)

tools/lib/atusb.c

@@ -31,13 +31,13 @@
 static int error;
 
 
-int atusb_error(void)
+static int atusb_error(void *dsc)
 {
 	return error;
 }
 
 
-int atusb_clear_error(void)
+static int atusb_clear_error(void *dsc)
 {
 	int ret;
 
@@ -191,9 +191,11 @@ static int atusb_buf_read(void *dsc, void *buf, int size)
 
 
 struct atspi_driver atusb_driver = {
-	.name		= "atusb",
+	.name		= "USB",
 	.open		= atusb_open,
 	.close		= atusb_close,
+	.error		= atusb_error,
+	.clear_error	= atusb_clear_error,
 	.reset		= atusb_reset,
 	.reset_rf	= atusb_reset_rf,
 	.reg_write	= atusb_reg_write,