flasher: Unify flash setup functions

They almost perform the same codepath, so unify them.

This is in preparation for the upcoming libflash API change, they will
call the same setup function.

Change-Id: If41592f3dc0c5d98db34e7a25ef2f884b031695c
Signed-off-by: Joel Stanley <joel@jms.id.au>
1 file changed