staging: vt6656: rxtx.c s_uFillDataHead remove dead variables.

As result of patches
staging: vt6656: rxtx.c: s_uGetDataDuration remove First Frag or Mid Frag dead code
staging: vt6656: rxtx.c: s_uGetDataDuration remove dead variables.

variables uFragIdx, cbLastFragmentSize, uMACfragNum are dead.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>