docs: Grammar and spelling fixes

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20180612065150.21110-1-ville.skytta@iki.fi
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

docs/interop/qcow2.txt

@@ -326,8 +326,8 @@ in the image file.
 It contains pointers to the second level structures which are called refcount
 blocks and are exactly one cluster in size.
 
-Given a offset into the image file, the refcount of its cluster can be obtained
-as follows:
+Given an offset into the image file, the refcount of its cluster can be
+obtained as follows:
 
     refcount_block_entries = (cluster_size * 8 / refcount_bits)
 
@@ -365,7 +365,7 @@ The L1 table has a variable size (stored in the header) and may use multiple
 clusters, however it must be contiguous in the image file. L2 tables are
 exactly one cluster in size.
 
-Given a offset into the virtual disk, the offset into the image file can be
+Given an offset into the virtual disk, the offset into the image file can be
 obtained as follows:
 
     l2_entries = (cluster_size / sizeof(uint64_t))

docs/interop/vhost-user.txt

@@ -108,12 +108,12 @@ Depending on the request type, payload can be:
    IOVA: a 64-bit I/O virtual address programmed by the guest
    Size: a 64-bit size
    User address: a 64-bit user address
-   Permissions: a 8-bit value:
+   Permissions: an 8-bit value:
     - 0: No access
     - 1: Read access
     - 2: Write access
     - 3: Read/Write access
-   Type: a 8-bit IOTLB message type:
+   Type: an 8-bit IOTLB message type:
     - 1: IOTLB miss
     - 2: IOTLB update
     - 3: IOTLB invalidate