clk: bcm: Add Broadcom Hurricane 2 clock support

Add support for the Broadcom Hurricane 2 SoC clock controller. We can
re-use the existing iProc clock library since the SoC's architecture is
largely the same as its predecessors. For now, we just initialize the
iProc ARM PLL.

Acked-by: Jon Mason <jon.mason@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>