[llvm] [ARM][TableGen][MC] Change the ARM mnemonic operands to be optional for ASM parsing (PR #83436)

[Alfie Richards via llvm-commits]

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@@ -1768,7 +1768,7 @@ let isBranch = 1, isTerminator = 1, isBarrier = 1, isIndirectBranch = 1 in {
 
 // In Thumb1, "nop" is encoded as a "mov r8, r8". Technically, the bf00
 // encoding is available on ARMv6K, but we don't differentiate that finely.
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AlfieRichardsArm wrote:

We also still dont differentiate for ARMv6k

https://github.com/llvm/llvm-project/pull/83436