board/solidrun/mx6cubox: create boot.scr in TARGET_DIR/boot
There is no reason to create boot.scr in board/solidrun/mx6cubox and
later install it in TARGET_DIR/boot, leaving a stale file behind.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 9ddbd11620b5a01945a438085d45ef2131bad35f)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>