Merged in masayuki2009/nuttx.nuttx/lc823450_smp_test (pull request #557)

sched/sched: Remove DEBUGASSERT() in sched_mergepending()

Because this DEBUGASSERT() assumes that while loop executes only once.

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Approved-by: Gregory Nutt <gnutt@nuttx.org>