Avoid calling pcpu_init() simultaneously.

pcpu_init() updates queue, so cannot be called by multiple cores
at the same time

Obtained from:	Semihalf
Disable decoding windows with no FDT entry.

- On ARMADAXP B0 (GP development board) we are not able to use PCI due to
   whole 32-bit address space used by 4GB of RAM memory.
- Change is required to destroy unnecessary window to free address space
   for PCI and other devices
- Fix offset value for SDRAM decoding windows

Obtained from:	Semihalf
Correct comment about initial VA=>PA mapping