flash: samd: declare const data

Make the chip information lookup tables const (thanks to Spencer Oliver for
pointing this out).  Also fix spacing on one macro.  No functional changes.

Change-Id: I053c4951c2626b8aa4541a79673b500394ef08e8
Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-on: http://openocd.zylin.com/1874


Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>