mksquashfs: reader_read_file(), remove file_buffer->block = count

Remove the setting of file_buffer->block to the file block count.
This value is never used.

A little bit of Squashfs archaeology shows this was in the earliest version
of parallel Mksquashfs from 2006, and the value wasn't used then either!
It is high time it was removed.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
index 4e9f352..5e050ae 100644
--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -2129,7 +2129,6 @@
 		if(byte != expected)
 			goto restat;
 
-		file_buffer->block = count;
 		file_buffer->error = FALSE;
 		file_buffer->fragment = FALSE;