usb: gadget: fix usb_ep_align_maybe endianness and new usb_ep_align

USB spec specifies wMaxPacketSize to be little endian (as other properties),
so when using this variable in the driver we should convert to the current
CPU endianness if necessary.

This patch also introduces usb_ep_align() which does always returns the
aligned buffer size for an endpoint. This is useful to be used by USB requests
allocator functions.

Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

include/linux/usb/gadget.h

@@ -417,9 +417,21 @@ static inline struct usb_gadget *dev_to_usb_gadget(struct device *dev)
 #define gadget_for_each_ep(tmp, gadget) \
 	list_for_each_entry(tmp, &(gadget)->ep_list, ep_list)
 
+/**
+ * usb_ep_align - returns @len aligned to ep's maxpacketsize.
+ * @ep: the endpoint whose maxpacketsize is used to align @len
+ * @len: buffer size's length to align to @ep's maxpacketsize
+ *
+ * This helper is used to align buffer's size to an ep's maxpacketsize.
+ */
+static inline size_t usb_ep_align(struct usb_ep *ep, size_t len)
+{
+	return round_up(len, (size_t)le16_to_cpu(ep->desc->wMaxPacketSize));
+}
+
 /**
  * usb_ep_align_maybe - returns @len aligned to ep's maxpacketsize if gadget
- *	requires quirk_ep_out_aligned_size, otherwise reguens len.
+ *	requires quirk_ep_out_aligned_size, otherwise returns len.
  * @g: controller to check for quirk
  * @ep: the endpoint whose maxpacketsize is used to align @len
  * @len: buffer size's length to align to @ep's maxpacketsize
@@ -430,8 +442,7 @@ static inline struct usb_gadget *dev_to_usb_gadget(struct device *dev)
 static inline size_t
 usb_ep_align_maybe(struct usb_gadget *g, struct usb_ep *ep, size_t len)
 {
-	return !g->quirk_ep_out_aligned_size ? len :
-			round_up(len, (size_t)ep->desc->wMaxPacketSize);
+	return g->quirk_ep_out_aligned_size ? usb_ep_align(ep, len) : len;
 }
 
 /**