V4L/DVB (7609): em28xx-core: speed-up firmware load

em28xx-core.c:
 - Remove sleep in i2c message routine which slows down i2c by a factor
   10x.  Load time for BASE firmware went from 13s to .973s

Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>