1. add some comments for structures

2. refined doxgen format comments.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@6803 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Include/IndustryStandard/Usb.h

@@ -334,6 +334,7 @@ typedef enum {
 #pragma pack(1)
 ///
 /// Descriptor header for Report/Physical Descriptors
+/// HID 1.1, section 6.2.1
 ///
 typedef struct hid_class_descriptor {
   UINT8   DescriptorType;
@@ -343,6 +344,7 @@ typedef struct hid_class_descriptor {
 ///
 /// The HID descriptor identifies the length and type
 /// of subordinate descriptors for a device.
+/// HID 1.1, section 6.2.1
 ///
 typedef struct hid_descriptor {
   UINT8                         Length;