clk: bcm: Make COMMON_CLK_IPROC into a library

The broadcom clk driver Kconfig file selects and depends on the
COMMON_CLK_IPROC config for different SoC specific drivers. Let's
simplify this by always selecting the COMMON_CLK_IPROC config,
turning it into a set of library code. We still want to retain
the SoC specific options, so we leave those in place. Since we're
here we also drop COMMON_CLK dependency because that's implicitly
handled by including this file in drivers/clk/Kconfig in the
right place and also make CLK_BCM_KONA default to y on the
architecture it exists for instead of plain default y.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ray Jui <ray.jui@broadcom.com>
Cc: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>