Fix yosys build after MMU merge

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>

Makefile.synth

@@ -45,7 +45,7 @@ OPENOCD_DEVICE_CONFIG=openocd/LFE5UM5G-85F.cfg
 VHDL_FILES  = fpga/soc_reset.vhdl fpga/clk_gen_bypass.vhd decode_types.vhdl
 VHDL_FILES += common.vhdl wishbone_types.vhdl wishbone_debug_master.vhdl
 VHDL_FILES += wishbone_arbiter.vhdl cache_ram.vhdl utils.vhdl plru.vhdl
-VHDL_FILES += helpers.vhdl dcache.vhdl core_debug.vhdl fetch1.vhdl fetch2.vhdl
+VHDL_FILES += helpers.vhdl mmu.vhdl dcache.vhdl core_debug.vhdl fetch1.vhdl fetch2.vhdl
 VHDL_FILES += register_file.vhdl insn_helpers.vhdl multiply.vhdl divider.vhdl
 VHDL_FILES += logical.vhdl crhelpers.vhdl countzero.vhdl rotator.vhdl
 VHDL_FILES += ppc_fx_insns.vhdl execute1.vhdl decode1.vhdl cr_file.vhdl