cmake: Remove src/csp_endian.c from CMakeLists.txt
cmake: Remove src/csp_endian.c from CMakeLists.txt

This is a leftover from the commit 2aaee5d9346 "Add CMake support".
The csp_endian.c was remove by the commit 34b01d5acb58, but CMake
support commit wasn't up to date at the time of merge.

Signed-off-by: Yasushi SHOJI <afa9ca3be149447780c2f7b524d61ed3d3db63f9@spacecubics.com>

libcsp/libcsp,libcsp/libcsp