selftests/resctrl: Remove "malloc_and_init_memory" param from run_fill_buf()
run_fill_buf()'s malloc_and_init_memory parameter is always 1. There's
also duplicated memory init code for malloc_and_init_memory == 0 case
in fill_buf() which is unused.
Remove the malloc_and_init_memory parameter and the duplicated mem init
code.
While at it, fix also a typo in run_fill_buf() prototype's argument.