Xilinx: ARM: clk: Remove unsupported leaf clocks

Removing leaf clocks from the clock framework for which the
current drivers lack support for the common clock framework.
The original approach was to add the complete clock tree and call
clk_prepare() and clk_enable() in the clock init routine, if the
driver does not yet do this.
The drawback of this approach is, that we also enable clocks, which
may be inactive on default (e.g. the peripheral is not connected on a
board and would be disabled by the bootloader). This may lead
to unnecessary power consumption.

With this patch all leaf clocks for which the driver does not
call clk_prepare() and clk_enable() are removed from the clock
framework leaving their gates untouched. Once a driver is ported
to use the common clock framework its leaf clocks must be readded.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>