block: vhdx - fix comment typos in header, fix incorrect struct fields

VHDXPage83Data and VHDXParentLocatorHeader both incorrectly had their
MSGUID fields set as arrays of 16.  This is incorrect (it stems from
an early version where those fields were uint_8 arrays).  Those fields
were, up to this patch, unused.

Also, there were a couple of typos and incorrect wording in comments,
and those have been fixed up as well.
Signed-off-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/vhdx.h

@@ -58,7 +58,7 @@
 typedef struct VHDXFileIdentifier {
     uint64_t    signature;              /* "vhdxfile" in ASCII */
     uint16_t    creator[256];           /* optional; utf-16 string to identify
-                                           the vhdx file creator.  Diagnotistic
+                                           the vhdx file creator.  Diagnostic
                                            only */
 } VHDXFileIdentifier;
 
@@ -114,8 +114,8 @@ typedef struct QEMU_PACKED VHDXHeader {
                                            there is no valid log. If non-zero,
                                            log entries with this guid are
                                            valid. */
-    uint16_t    log_version;            /* version of the log format. Mustn't be
-                                           zero, unless log_guid is also zero */
+    uint16_t    log_version;            /* version of the log format. Must be
+                                           set to zero */
     uint16_t    version;                /* version of the vhdx file.  Currently,
                                            only supported version is "1" */
     uint32_t    log_length;             /* length of the log.  Must be multiple
@@ -281,7 +281,7 @@ typedef struct QEMU_PACKED VHDXVirtualDiskSize {
 } VHDXVirtualDiskSize;
 
 typedef struct QEMU_PACKED VHDXPage83Data {
-    MSGUID      page_83_data[16];       /* unique id for scsi devices that
+    MSGUID      page_83_data;           /* unique id for scsi devices that
                                            support page 0x83 */
 } VHDXPage83Data;
 
@@ -296,7 +296,7 @@ typedef struct QEMU_PACKED VHDXVirtualDiskPhysicalSectorSize {
 } VHDXVirtualDiskPhysicalSectorSize;
 
 typedef struct QEMU_PACKED VHDXParentLocatorHeader {
-    MSGUID      locator_type[16];       /* type of the parent virtual disk. */
+    MSGUID      locator_type;           /* type of the parent virtual disk. */
     uint16_t    reserved;
     uint16_t    key_value_count;        /* number of key/value pairs for this
                                            locator */