media: tw68: fix kernel-doc markups

There are a few mistakes on the existing markups:

  drivers/media/pci/tw68/tw68-risc.c:32: warning: Cannot understand  *  @rp		pointer to current risc program position
   on line 32 - I thought it was a doc line
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'pci'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'buf'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'sglist'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'top_offset'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'bottom_offset'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'bpl'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'padding'
  drivers/media/pci/tw68/tw68-risc.c:144: warning: No description found for parameter 'lines'

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>