Hello,
.ld is the linker file extension for GNU ARM compiler (well, linker), while .lcf is for the proprietary Freescale ARM compiler/linker.
In CW for MCU you can choose at project creation time if you want to use the (legacy) Freescale ARM compiler, or the GNU compiler. The GNU compiler is the default and recommended. And for Kinetis L there is only GNU supported.
I hope this helps?