Blackfin: cm-bf537e/cm-bf537u/tcm-bf537: update embedded env settings

The recent commit ea882baf broke embedding environments in the middle
of a sector, so relocate it to the start of the 2nd sector.

Signed-off-by: Harald Krapfenbauer <harald.krapfenbauer@bluetechnix.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>