scripts: elf_helper.py: Simplify tests with chained comparisons

'a < b and b < c' can be simplified to 'a < b < c' in Python.

Fixes this pylint warning:

    R1716: Simplify chained comparison between the operands
    (chained-comparison)

Fixing pylint warnings for a CI check.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>