scripts/faddr2line: Reduce number of readelf calls to three

Rather than calling readelf several times for each invocation of
__faddr2line, call readelf only three times at the beginning, and save its
result for future use.

Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com>
Link: https://lore.kernel.org/r/20240415145538.1938745-2-bjohannesmeyer@gmail.com


Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>