mmc: sdhci-sirf: add mmc host sdhci-pltfm based driver for SiRF SoCs

This patch adds the new driver for CSR SiRF SoCs:

SiRFprimaII: unicore ARM Cortex-A9
SiRFatlas6: unicore ARM Cortex-A9
SiRFmarco: dual core ARM Cortex-A9 SMP

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Bin Shi <Bin.Shi@csr.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Chris Ball <cjb@laptop.org>