Fix warnings in acl_threadsupport

[pcolberg]

Warnings from Ubuntu 22.04 debug build with GCC 11.2:

• lib/acl_threadsupport/src/acl_threadsupport.c

  [76/113] /usr/bin/gcc -DNOMINMAX -I/__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/include -g -fPIC -Wall -Wconversion -Wformat -Wformat-security -fno-strict-aliasing -fstack-protector -D_FORTIFY_SOURCE=2 -Og -MD -MT lib/acl_threadsupport/CMakeFiles/acl_threadsupport.dir/src/acl_threadsupport.c.o -MF lib/acl_threadsupport/CMakeFiles/acl_threadsupport.dir/src/acl_threadsupport.c.o.d -o lib/acl_threadsupport/CMakeFiles/acl_threadsupport.dir/src/acl_threadsupport.c.o -c /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c
  /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c: In function 'acl_set_process_affinity_mask':
  /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c:125:7: warning: conversion to 'size_t' {aka 'long unsigned int'} from 'int' may change the sign of the result [-Wsign-conversion]
    125 |       CPU_SET(i, &mask);
        |       ^~~~~~~
  /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c: In function 'acl_timed_wait_condvar':
  /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c:427:31: warning: conversion to 'unsigned int' from 'int' may change the sign of the result [-Wsign-conversion]
    427 |     C->timedout[my_entry_q] = timed_out;
        |                               ^~~~~~~~~
  /__w/fpga-runtime-for-opencl/fpga-runtime-for-opencl/lib/acl_threadsupport/src/acl_threadsupport.c:442:17: warning: conversion to 'int' from 'unsigned int' may change the sign of the result [-Wsign-conversion]
    442 |     timed_out = C->timedout[my_entry_q];
        |                 ^