perf jit: Fix inaccurate DWARF line table

Fix an issue where addresses in the DWARF line table are offset by -0x40
(GEN_ELF_TEXT_OFFSET). This can be seen with `objdump -S` on the ELF
files after perf inject.

Committer notes:

Ian added this in his Acked-by reply:

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Without too much knowledge this looks good to me. The original code came
from oprofile's jit support:

  https://sourceforge.net/p/oprofile/oprofile/ci/master/tree/opjitconv/debug_line.c#l325


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Signed-off-by: Nick Gasson <nick.gasson@arm.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200528051916.6722-1-nick.gasson@arm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>