V4L/DVB (7813): Fix compilation, when V4L1_COMPAT is disabled

This driver uses some sysfs helper functions that are available only for legacy
drivers. It also requires linux/mm.h.

This patch fixes compiliation when not in compat mode.

Thanks to Ingo Molnar for identifying this issue.

Acked-by: Jaime Velasco Juan <jsagarribay@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>