Hi,
you can use both PLL or crystal oscillator clock. But it is recommended to use crystal oscillator, because it has better jitter. Basic information about PLL jitter you find in the Datasheet rev.8 on the page 71.
http://cache.nxp.com/files/32bit/doc/data_sheet/MPC5607B.pdf?fsrch=1&sr=1&pageNum=1
Regards,
Martin