clk: socfpga: Add a clk-phase property to the "altr,socfpga-gate-clk"

clk: socfpga: Add a clk-phase property to the "altr,socfpga-gate-clk"

The clk-phase property is used to represent the 2 clock phase values that is
needed for the SD/MMC driver. Add a prepare function to the clk_ops, that will
use the syscon driver to set sdmmc_clk's phase shift that is located in the
system manager.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Acked-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
---
v9: none
v8: Use degrees in the clk-phase binding property
v7: Add dts property to represent the clk phase of the sdmmc_clk. Add a
    prepare function to the gate clk that will toggle clock phase setting.
    Remove the "altr,socfpga-sdmmc-sdr-clk" clock type.
v6: Add a new clock type "altr,socfpga-sdmmc-sdr-clk" that will be used to
    set the phase shift settings.
v5: Use the "snps,dw-mshc" binding
v4: Use the sdmmc_clk prepare function to set the phase shift settings
v3: Not use the syscon driver because as of 3.13-rc1, the syscon driver is
    loaded after the clock driver.
v2: Use the syscon driver