programs/suspend/parse: resolve rubocop Metrics/BlockNesting issue

[rli9]

Reproduce

lkp-tests$ rubocop programs/suspend/parse
Inspecting 1 file
C

Offenses:

programs/suspend/parse:34:7: C: Metrics/BlockNesting: Avoid more than 3 levels of block nesting.
      if stage == 'begin' ...
      ^^^^^^^^^^^^^^^^^^^
programs/suspend/parse:41:7: C: Metrics/BlockNesting: Avoid more than 3 levels of block nesting.
      if stage == 'end' ...
      ^^^^^^^^^^^^^^^^^
programs/suspend/parse:47:15: C: Metrics/BlockNesting: Avoid more than 3 levels of block nesting.
      phase = if stage == 'begin' ...
              ^^^^^^^^^^^^^^^^^^^

Reference
https://github.com/intel/lkp-tests/wiki/Coding-Standard#rubocop