Retire -E's "expert" mode. Introduced 23 years ago to avoid
confusing users with FFS attributes that only experts should
fiddle with. Actual use has withered away with functionality
rendered moot or moved elsewhere.

'-e' remains for the truly obscure corner cases.

Simply excise the code for now to see if hidden users/uses are
exposed. Further simplifications are possible if no such
users/uses surface.

ok with sthen@ millert@ kn@ otto@

Create & use variables MRDISKTYPE and MRMAKEFSARGS like all the other build
makefiles.

Fixes & ok kn@

No intentional functional change.

Add missing dependency.

First stab at a bootloader for OpenBSD/powerpc64.
Based on the same principle (and mostly copied from) the bootloader
written by visa@ for OpenBSD/octeon.

Needed because the petitboot environment provided by the OpenPower
firmware is unsuitable for loading OpenBSD kernels properly.

Create & use variables MRDISKTYPE and MRMAKEFSARGS like all the other build
makefiles.

Fixes & ok kn@

No intentional functional change.

Add missing dependency.

First stab at a bootloader for OpenBSD/powerpc64.
Based on the same principle (and mostly copied from) the bootloader
written by visa@ for OpenBSD/octeon.

Needed because the petitboot environment provided by the OpenPower
firmware is unsuitable for loading OpenBSD kernels properly.