arm64: uaccess: remove vestigal UAO support

mainline inclusion
from mainline-v5.11-rc1
commit 1517c4fa
category: performance
bugzilla: https://e.gitee.com/open_euler/issues/list?issue=I4SCW7


CVE: NA

-------------------------------------------------------------------------

Now that arm64 no longer uses UAO, remove the vestigal feature detection
code and Kconfig text.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-13-mark.rutland@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>