arch/riscv: remove misaligned load/store/fetch handling

Testing on the unmatched shows the code no longer works completely
correctly; Linux has taken over the handling of misalignment
anyway, because handling it in firmware, with the growing
complexity of the ISA and the awkward way in which it
has to be handled, is more trouble than its worth.

Plus, we don't WANT misalignment handled, magically, in
firmware: the cost of getting it wrong is high (as I've
spent a month learning); the performance is terrible (350x
slowdown; and most toolchains now know to avoid unaligned
load/store on RISC-V anyway.

But, mostly, if alignment problems exist, *we need to know*,
and if they're handled invisibly in firmware, we don't.

The problem with invisible handling was shown a while back
in the Go toolchain: runtime had a small error, such that
many misaligned load/store were happening, and it was
not discovered for some time. Had a trap been directed
to kernel or user on misalignment, the problem would
have been known immediately, not after many months.
(The error, btw, was masking the address with 3,
not 7, to detect misalignment; an easy mistake!).

But, the coreboot code does not work any more any way,
and it's not worth fixing. Remove it.

Tested by booting Linux to runlevel 1; before,
it would hang on an alignment fault, as the
alignment code was failing (somewhere).

This takes the coreboot SBI code much closer to
revival.

Change-Id: I84a8d433ed2f50745686a8c109d101e8718f2a46
Signed-off-by: Ronald G Minnich <rminnich@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81416
Reviewed-by: Maximilian Brune <maximilian.brune@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

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