Calling nand_do_upgrade() from platform_pre_upgrade() was obsoleted in
the commit 30f61a34b4 ("base-files: always use staged sysupgrade").
This change brings bcm53xx in sync with other targets and allows
dropping backward compatibility code. It shouldn't change any user
visible behavior.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
ccf8a8e863