Pthread

[ffainelli]

Fixes the following build warning:

In file included from busy.c:3: /home/buildroot/instance-0/output-1/host/mips-buildroot-linux-uclibc/sysroot/usr/include/pthread.h:164:36: note: expected 'void * (*)(void )' but argument is of type 'void * ()(void)' 164 | void (__start_routine) (void *), | ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~ busy.c:6:7: note: 'loop' declared here 6 | void *loop() | ^~~~