dmaengine/amba-pl08x: Take flow controller info from DMA_SLAVE_CONFIG

Flow controller information is passed now from DMA_SLAVE_CONFIG option. This
patch makes changes in pl08x driver to use device_fc from it instead of platform
data.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>