timers/migration: Clean up the loop in tmigr_quick_check()

timers/migration: Clean up the loop in tmigr_quick_check()

Make the logic easier to follow:

  - Remove the final return statement, which is never reached, and move the
    actual walk-terminating return statement out of the do-while loop.

  - Remove the else-clause to reduce indentation. If a non-lonely group is
    encountered during the walk, the loop is immediately terminated with a
    return statement anyway; no need for an else.

Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250606124818.455560-1-ptesarik@suse.com