spi: sirf: refactor spi transfer functions
spi: sirf: refactor spi transfer functions

split sirfsoc_spi_transfer function into 3 sub-functions:
spi_sirfsoc_cmd_transfer, spi_sirfsoc_pio_transfer and
spi_sirfsoc_dma_transfer.

Signed-off-by: Qipan Li <7edc63b2168f7aeebdbedbd3916b18244ee96ac4@csr.com>
Signed-off-by: Barry Song <a856445693a373abed3e477bd705f7011cbd8a1d@csr.com>
Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs