V4L/DVB (7746): pvrusb2: make signed one-bit bitfields unsigned

Single-bit signed bitfields can only take 0/-1 rather than 0/1 as the
drivers seems to assume...add unsigned.
Noticed by sparse:
drivers/media/video/pvrusb2/pvrusb2-devattr.h:107:34: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:114:37: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:117:30: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:120:23: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:124:24: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:128:23: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:138:36: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:143:24: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:144:28: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:145:26: error: dubious one-bit signed bitfield
drivers/media/video/pvrusb2/pvrusb2-devattr.h:146:23: error: dubious one-bit signed bitfield

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>