staging: emxx_udc: allow modular build

A change to the usb gadget core allowed certain API functions to be
part of a loadable module, which breaks having emxx_udc built-in:

drivers/staging/built-in.o: In function `nbu2ss_drv_probe':
(.text+0x2428): undefined reference to `usb_ep_set_maxpacket_limit'

The original patch already fixed tons of other cases that have the
added dependency but apparently missed this one that now appears
in an ARM allmodconfig build.

This patch makes the symbol "tristate", which lets the Kconfig
dependency tracking handle it correctly. To make the module
actually usable, I also revert 0af61e66ee16 ("drivers/staging:
make emxx_udc.c explicitly non-modular"), which Paul Gortmaker
added after noticing that the Kconfig symbol was 'bool'.
Compared to the original version however, I leave out the
'__exit' annotation on the remove callback, as Paul pointed
out that this was incorrect.

Signed-off-by: Arnd Bergmann <[e-mail]>
Fixes: 5a8d651a2bde ("usb: gadget: move gadget API functions to udc-core")
Acked-by: Felipe Balbi <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/emxx_udc/Kconfig

···
 config USB_EMXX
-	bool "EMXX USB Function Device Controller"
+	tristate "EMXX USB Function Device Controller"
  	depends on USB_GADGET && (ARCH_SHMOBILE || (ARM && COMPILE_TEST))
 	help
 	   The Emma Mobile series of SoCs from Renesas Electronics and

drivers/staging/emxx_udc/emxx_udc.c

···
  */
 
 #include <linux/kernel.h>
-#include <linux/init.h>
+#include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/ioport.h>
···
 
 #include "emxx_udc.h"
 
+#define	DRIVER_DESC	"EMXX UDC driver"
 #define	DMA_ADDR_INVALID	(~(dma_addr_t)0)
 
 static const char	driver_name[] = "emxx_udc";
+static const char	driver_desc[] = DRIVER_DESC;
 
 /*===========================================================================*/
 /* Prototype */
···
 }
 
 /*-------------------------------------------------------------------------*/
+static int nbu2ss_drv_remove(struct platform_device *pdev)
+{
+	struct nbu2ss_udc	*udc;
+	struct nbu2ss_ep	*ep;
+	int	i;
+
+	udc = &udc_controller;
+
+	for (i = 0; i < NUM_ENDPOINTS; i++) {
+		ep = &udc->ep[i];
+		if (ep->virt_buf)
+			dma_free_coherent(NULL, PAGE_SIZE,
+				(void *)ep->virt_buf, ep->phys_buf);
+	}
+
+	/* Interrupt Handler - Release */
+	free_irq(INT_VBUS, udc);
+
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
 static int nbu2ss_drv_suspend(struct platform_device *pdev, pm_message_t state)
 {
 	struct nbu2ss_udc	*udc;
···
 static struct platform_driver udc_driver = {
 	.probe		= nbu2ss_drv_probe,
 	.shutdown	= nbu2ss_drv_shutdown,
+	.remove		= nbu2ss_drv_remove,
 	.suspend	= nbu2ss_drv_suspend,
 	.resume		= nbu2ss_drv_resume,
 	.driver		= {
-		.name			= driver_name,
-		.suppress_bind_attrs	= true,
+		.name	= driver_name,
 	},
 };
 
-builtin_platform_driver(udc_driver);
+module_platform_driver(udc_driver);
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_AUTHOR("Renesas Electronics Corporation");
+MODULE_LICENSE("GPL");