net: ethernet: ti: cpts: fix build failure for powerpc

Add dependency to TI CPTS from Common CLK framework COMMON_CLK to fix
allyesconfig build for Powerpc:

drivers/net/ethernet/ti/cpts.c: In function 'cpts_of_mux_clk_setup':
drivers/net/ethernet/ti/cpts.c:567:2: error: implicit declaration of function 'of_clk_parent_fill'; did you mean 'of_clk_get_parent_name'? [-Werror=implicit-function-declaration]
  of_clk_parent_fill(refclk_np, parent_names, num_parents);
  ^~~~~~~~~~~~~~~~~~
  of_clk_get_parent_name

Fixes: a3047a81

 ("net: ethernet: ti: cpts: add support for ext rftclk selection")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>