Insert missing break in hwintrinsicarm64.cpp

[Gnbrkm41]

In my previous PR to introduce / vectorise Vector{Size}<T>.AllBitsSet / Zero
(#33924), there was a missing break; in a switch statement in the importation logic, which resulted in the correct functions not being imported as GT_HWINTRINSIC nodes as the control fell through the default block, returning nullptr (meaning the method is not a valid HWINTRINSIC node and should be imported as regular function).

This was pointed out in #35300 (comment) by @echesakovMSFT, where Vector128.CreateScalar methods were found out to be using the software fallback.

JitDump of the importation part, prior to this change:

    [ 0]  10 (0x00a) call 0A00007D
In Compiler::impImportCall: opcode is call, kind=0, callRetType is struct, structSize is 8
Named Intrinsic System.Runtime.Intrinsics.Vector64`1.get_Zero: Notify VM instruction set (Vector64) must be supported.
Recognized
  Known type Vector64<int>
  Known type Vector64<int>
  Known type Vector64<int>


               [000039] I-C-G-------              ▌  CALL      simd8  System.Runtime.Intrinsics.Vector64`1[Int32][System.Int32].get_Zero (exactContextHnd=0x0000FFFF11276419)

JitDump of the importation part, after this change:

    [ 0]  10 (0x00a) call 0A00007D
In Compiler::impImportCall: opcode is call, kind=0, callRetType is struct, structSize is 8
Named Intrinsic System.Runtime.Intrinsics.Vector64`1.get_Zero: Notify VM instruction set (Vector64) must be supported.
Recognized
  Known type Vector64<int>
  Known type Vector64<int>

    [ 1]  15 (0x00f) stloc.0
lvaGrabTemp returning 4 (V04 tmp3) (a long lifetime temp) called for Inline stloc first use temp.
  Known type Vector64<int>


               [000041] -A----------              ▌  ASG       simd8  (copy)
               [000039] D------N----              ├──▌  LCL_VAR   simd8 <System.Runtime.Intrinsics.Vector64`1[Int32]> V04 tmp3
               [000038] ------------              └──▌  HWINTRINSIC simd8  int get_Zero

(I'm so sorry for missing this out, I think the build I was testing with before was somehow outdated)

[echesakov]

Thanks for fixing this!