Motion-PRO: Update configuration to accomodate next generation board.

New board has faster oscillator and a different Flash chip. This affects:
- CFG_MPC5XXX_CLKIN
- SDRAM timings
- Flash CS configuration (timings)
- Flash sector size, and thus MTD partition layout
- malloc() arena size (due to bigger Flash sectors)
- smaller memory test range (due to bigger malloc() arena)

This patch also enables more extensive memory testing via "mtest".

Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>