arm64 v4.19.y LLVM_IAS=y patches

Dear stable kernel maintainers, Please consider applying the following backports of commit e0d5896bd356 ("arm64: lse: fix LSE atomics with LLVM's integrated assembler") which first landed in v5.6-rc1 and was already picked up into linux-5.4.y as f68668292496 in v5.4.22 (adjusted for a conflict due to commit addfc38672c7 ("arm64: atomics: avoid out-of-line ll/sc atomics") which landed in v5.4-rc1).

Also contains a fix for that first patch which cherry-picks cleanly, commit dd1f6308b28e ("arm64: lse: Fix LSE atomics with LLVM").

The attached patches allow for Android and CrOS to build with LLVM_IAS=1 for arm64 for v4.19.y (modulo one small patch that I will send tomorrow).