clk: iproc: Make clocks visible options

Make the clocks visible options that can be selected by anyone.  This
avoids the problems of:
 1) Select is a reverse dependency and is hard for people to understand
    and can sometimes be a pain to track down
 2) Build coverage goes down because configs are hidden
 3) Code bloat

Patch suggested by Stephen Boyd

Signed-off-by: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>