spi: sirf: reset SPI controller in init stage

in SPI boot mode, romcode uses SPI controller to fetch data from NOR
flash. Here we need to reset the hardware IP to restore its state.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Mark Brown <broonie@kernel.org>