clk: hi6220: Add the hi655x's pmic clock

The hi655x multi function device is a PMIC providing regulators.

The PMIC also provides a clock for the WiFi and the Bluetooth, let's implement
this clock in order to add it in the hi655x MFD and allow proper wireless
initialization.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
[sboyd@codeaurora.org: Remove clkdev usage]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>