install: embed_firmware: use correct suffix
Embed the firmware from the right chroot suffix. Previously it would always use the rootfs_{args.device} chroot, which does not work anymore with upcoming 'pmbootstrap install --ondev --no-rootfs' (#1966 (closed)) as there will only be the installer_{args.device} chroot.
How to test
- Run
pmbootstrap install
with a device usingdeviceinfo_sd_embed_firmware
(e.g. PinePhone, Librem 5). It should work the same as before.