powerpc/fsl: remove the PPC_CLOCK dependency

Config FSL_SOC does not depend on PPC_CLOCK anymore since the following
commit got merged: 93abe8e4 (clk: add non CONFIG_HAVE_CLK routines)
Config CPM does not use PPC_CLOCK either currently. So remove them.

PPC_CLOCK also keeps Freescale PowerPC archtecture from supporting COMMON_CLK.

Signed-off-by: Tang Yuantian <Yuantian.Tang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>