[media] cx88: Remove duplicate const

[media] cx88: Remove duplicate const

This patch fixes the following sparse warnings
by removing use of duplicate const.

drivers/media/video/cx88/cx88.h:152:40:
	warning: duplicate const
drivers/media/video/cx88/cx88-core.c:256:33:
	warning: duplicate const
drivers/media/video/cx88/cx88-alsa.c:769:41:
	warning: duplicate const

As commented by Jonathan Nieder:

	These double "const" were introduced in v2.6.37-rc1~64^2~464 (V4L/DVB:
	drivers/media: Make static data tables and strings const, 2010-08-25).

	The address of an array is already immutable by definition, so for
	what it's worth, with or without a clarified commit message,

[mchehab@redhat.com: Tested with "gcc -s" (version 4.7.0):
 the produced asm is indeed equal before and after this patch]
Signed-off-by: Emil Goode <emilgoode@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>