perf symbols: Fix map->end fixup

When synthesizing maps from files that have incomplete symbol
information, like kallsyms, we need to fixup the end of maps by seting
its end from the ->start of the next map, fix it to set prev_map->end to
curr_map->start, since ->end is the first byte outside prev_map address
range.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-ivbrj08sjakxdwkrcndbkoig@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>