MTD: Convert Atmel PRI information to AMD format

Atmel flash chips don't have PRI information in the same format as
AMD flash chips. This patch installs a fixup for all Atmel chips that
converts the relevant PRI fields into AMD format.

Only the fields that are actually used by the command set is actually
converted. The rest are initialized to zero (which should be safe)

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>