media: cxd2880: Add spi device IO routines

Add functions for initializing, reading and writing to the SPI
device for the Sony CXD2880 DVB-T2/T tuner + demodulator.

Signed-off-by: Yasunari Takiguchi <Yasunari.Takiguchi@sony.com>
Signed-off-by: Masayuki Yamamoto <Masayuki.Yamamoto@sony.com>
Signed-off-by: Hideki Nozawa <Hideki.Nozawa@sony.com>
Signed-off-by: Kota Yonezawa <Kota.Yonezawa@sony.com>
Signed-off-by: Toshihiko Matsumoto <Toshihiko.Matsumoto@sony.com>
Signed-off-by: Satoshi Watanabe <Satoshi.C.Watanabe@sony.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>