tools: hv: fcopy_daemon: support >2GB files for x86_32 guest

Without this patch, hv_fcopy_daemon's hv_copy_data() -> pwrite()
will fail for >2GB file offset.

The current char-next branch is broken and this patch fixes
the bug.

Signed-off-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>