processes plugin: const correctness

processes plugin: const correctness

src/processes.c: In function ‘ps_submit_proc_list’:
src/processes.c:915:8: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       {"delay-cpu", ps->delay_cpu},
        ^~~~~~~~~~~
src/processes.c:916:8: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       {"delay-blkio", ps->delay_blkio},
        ^~~~~~~~~~~~~
src/processes.c:917:8: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       {"delay-swapin", ps->delay_swapin},
        ^~~~~~~~~~~~~~
src/processes.c:918:8: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
       {"delay-freepages", ps->delay_freepages},
        ^~~~~~~~~~~~~~~~~