ANDROID: sched: pelt: Fix the PELT arrays

Commit 8d420888 ("ANDROID: sched: Add PELT cmdline arg") removed the
'__maybe_unused' and 'const' qualifiers from the declaration of the PELT
arrays for no apparent reason.

Re-introduce both of them to silence the 'Maybe unused' warnings and
align as much as possible with upstream.

Bug: 177593580
Fixes: 8d420888 ("ANDROID: sched: Add PELT cmdline arg")
Signed-off-by: Quentin Perret <qperret@google.com>
Change-Id: I5416726a285eff881ba7bc5188f8a69ee40b1f99