staging: vt6656: Fix inconsistent structure packing

vt6656 has several headers that use the #pragma pack(1) directive to
enable structure packing, but never disable it.  The layout of
structures defined in other headers can then depend on which order the
various headers are included in, breaking the One Definition Rule.

In practice this resulted in crashes on x86_64 until the order of header
inclusion was changed for some files in commit 11d404cb

 ('staging:
vt6656: fix headers and add cfg80211.').  But we need a proper fix that
won't be affected by future changes to the order of inclusion.

This removes the #pragma pack(1) directives and adds __packed to the
structure definitions for which packing appears to have been intended.

Reported-and-tested-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>