staging: ft1000: Pseudo header handlig improved.

Handling for pseudo header was done by directly copying
data to tx buffer. This hide a functionality and make
code unreadable.

Use approach where fill pseudo_hdr structure first with data and then copy
to beginning of buffer.

Signed-off-by: Marek Belisko <marek.belisko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>