Misc Cortex-A5 changes include new file for cache operations
A few more Cortex-A5 and SAMA5 files
Add some preliminary linker scripts in order to begin building the SAMA5 target
Add system timer logic for the SAMA5
SAMA5/Cortex-A: Improve irqsave/restore inlines + add irqenable.  Add skeleton file for SAMA5 interrupt management.  Also change from last commit that was left in the editor
Merge branch 'master' of http://git.code.sf.net/p/nuttx/git into leach