Using ONESHOT_CURRENT retrieves the tick number multiplied by tick time; thus
it doesn't give the accurate monotonic time - it is quantized by
the tick time. This cannot be used as a ndelay timer, it would always loop
at least to the end of the ongoing tick.
Revert the up_udelay to use the original "coarse" looping. The "accurate" udelay,
if such is needed, should either be done under arch specific code, or there should be
a function for getting the accurate time that is available for all the platforms.
Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>