arch: Moved atmel_sam3 to atmel_sam3x.

Found out that the SAM3 series is not a single series. There are actully
3 different series, 3U, 3A, and 3X.

Origin: Original
Jira: ZEP-2067

Change-Id: I61cdc826cc32dbdd25b5e6bafaada062c8ae8417
Signed-off-by: Justin Watson <jwatson5@gmail.com>
8 files changed