clk: Add Gemini SoC clock controller

The Cortina Systems Gemini (SL3516/CS3516) has an on-chip clock
controller that derive all clocks from a single crystal, using some
documented and some undocumented PLLs, half dividers, counters and
gates. This is a best attempt to construct a clock driver for the
clocks so at least we can gate off unused hardware and driver the
PCI bus clock.

Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[sboyd@codeaurora.org: Fix devm_ioremap_resource() return value
checking]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>