vybrid: Fix hardware clock drift

We must enable the external 32kHz oscillator in order to work
around a known clock drift issue with the internal 32kHz oscillator.

This fixes the Linux kernel system clock drift.

Signed-off-by: Anthony Huereca <B04178@freescale.com>
Signed-off-by: Jiri Kotzian <B36968@freescale.com>
Signed-off-by: Justin Waters <justin.waters@timesys.com>