mx51 and mx53 are device tree only platforms, so we no longer need all these
calls to clk_register_clkdev().

Only keep cpu0 and gpc_dvfs clk_register_clkdev() calls.

Tested on imx51-babbage and imx53-qsb boards.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@freescale.com>