Merged in masayuki2009/nuttx.nuttx/lc823450_smp_test (pull request #601)

lc823450 smp test

* sched/clock: Replace critical section APIs with spin lock APIs in clock_gettime.c

    This change will improve performance for SMP systems but nothing
    changes for non-SMP systems. (Pls see include/nuttx/irq.h)

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

* sched/sched: Remove unnecessary DEBUGASSERT in sched_removereadytorun.c

    In SMP mode, rtrtcb is not always at the g_readytorun.head.
    This change removes DEBUGASSERT() to avoid this condition.

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

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