MGS-896 [#1818] Kernel panic when run mesa_copytex on 6qp board

After enable dynamic mmu mapping, all the address should be mapped
dynamically including the address located in static mapping region.
Since the static mapping is linear, the upper function can use the
mapped address as the physical address. However dynamic mapping break
this rule and cause some issues.

To keep the rule still work, limit dynamic mapping happens over the mmu
dynamic start address.

Date July 27, 2015

Signed-off-by: Shawn Xiao <b49994@freescale.com>