arch-x86: Remove __init__ from the X86MicrocodeRom class.

This is just setting up an empty dict the base class already sets up.

Change-Id: I22b00799f3424f9ced784c3d25771b979865e53d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56329
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/x86/isa/rom.isa

@@ -41,10 +41,6 @@ let {{
     from micro_asm import Rom
 
     class X86MicrocodeRom(Rom):
-        def __init__(self, name):
-            super().__init__(name)
-            self.directives = {}
-
         def add_microop(self, mnemonic, microop):
             microop.mnemonic = mnemonic
             microop.micropc = len(self.microops)