perf tools mips: Fix mips syscall generation

The mips syscall generation was still based on the old method. Delete
the Makefile since it is no longer needed with the new method of
generation.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Fixes: 619ffe6 ("perf tools mips: Use generic syscall scripts")
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250110-perf_fix_mips-v1-1-4e661c3b710a@rivosinc.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: charlie-rivos