V4L/DVB (7384): tda18271: store FM_RFn setting in struct tda18271_std_map_item

All standard related configuration is stored within
struct tda18271_std_map_item.  Pass a pointer to this
structure rather than its individual members.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>