arm64: insn: remove BUG_ON from codegen

During code generation, we used to BUG_ON unknown/unsupported encoding
or invalid parameters.

Instead, now we report these as errors and simply return the
instruction AARCH64_BREAK_FAULT. Users of these codegen helpers should
check for and handle this failure condition as appropriate.

Otherwise, unhandled codegen failure will result in trapping at
run-time due to AARCH64_BREAK_FAULT, which is arguably better than a
BUG_ON.

Change-Id: I35f8d8960c0a3f6cecf0690e8f93fce339ed8838
Git-commit: c94ae4f7c5ec6b6fddde1c08809d5e32a963d7f3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Runmin Wang <runminw@codeaurora.org>