perf annotate: Fix multiple memory and file descriptor leaks

Store SYMBOL_ANNOTATE_ERRNO__BPF_MISSING_BTF in variable *ret*, instead
of returning in the middle of the function and leaking multiple
resources: prog_linfo, btf, s and bfdf.

Addresses-Coverity-ID: 1454832 ("Structurally dead code")
Fixes: 11aad897

 ("perf annotate: Don't return -1 for error when doing BPF disassembly")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191014171047.GA30850@embeddedor
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>