While checking all gspca sub drivers pkt_scan functions for a bug I found in
1 of them (and after checking also in another), I noticed a bug in the
gspca_jeilinj work queue function, once it has decided to start discard a
frame because the application is not reading fast enough (and thus returning
buffers to fill fast enough), it never stops discarding.

This patch fixes this by simply completely removing the "discarding"
variable, if we need to discard the current frame because there is no buffer
to store it, the "frame" pointer will be NULL, so that is all we need to
check.

I've also moved the gspca_get_i_frame() call and the writing of the jpg
header to the buffer to after the first usb_bulk_msg() call, as we don't
need it before that, and that will give the app slightly more time to
queue a buffer for us to fill.
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>