vboot/vboot_common: actually provide a writable region_device
vboot_named_region_device_rw() is supposed to provide a writable
region_device. However, it was calling fmap_locate_area_as_rdev()
which only provides a read-only one. Fix this.
BUG=chrome-os-partner:56151
Change-Id: I6279fde32132b1b6138292c3ef771c59709e00c6
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16302
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>