AArch64: V28 register mismangled as the stolen X28 register

Created by: zhoubot

It seems the instr_uses_reg(instr, dr_reg_stolen) is not returning the correct result for instructions that use SIMD registers. Presumably there is a bug in the decoder.

As a result, I've found the unessessary mangles in the DynamoRIO AArch64 7.0.0-RC1 release:

      fmov d28, d12

is manged to

      str    x1, [x28,#8]     
      mov    x1, x28          
      ldr    x28, [x28,#48]   
      fmov   d28, d12         
      str    x28, [x1,#48]    
      mov    x28, x1          
      ldr    x1, [x28,#8]