We are reverting the changes in commit
55b3f05932 given build errors are seen
when fcntl.h is included, as it declares fcntl() as a non-static
function. The same function cannot be declared as both static and
non-static.
Instead, we avoid redefining fcntl() in lib/os/fdtable.c specifically
for case of the SimpleLink family, til we have support for the new
socket_op_vtable.
Signed-off-by: Vincent Wan <vincent.wan@linaro.org>