arm64: cpufeatures: Add capability for LDAPR instruction

mainline inclusion
from mainline-v5.11-rc1
commit 364a5a8a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7LP2Z

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=364a5a8ae8dc2dd457e2fefb4da3f3fd2c0ba8b1



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Armv8.3 introduced the LDAPR instruction, which provides weaker memory
ordering semantics than LDARi (RCpc vs RCsc). Generally, we provide an
RCsc implementation when implementing the Linux memory model, but LDAPR
can be used as a useful alternative to dependency ordering, particularly
when the compiler is capable of breaking the dependencies.

Since LDAPR is not available on all CPUs, add a cpufeature to detect it at
runtime and allow the instruction to be used with alternative code
patching.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

conflict:
	arch/arm64/Kconfig
	arch/arm64/include/asm/cpucaps.h
	arch/arm64/kernel/cpufeature.c
Signed-off-by: Zeng Heng <zengheng4@huawei.com>