fpga/Makefile: *.mif_update.rpt isn't a terminal target

The problem that made it need to be specified as one has been fixed,
so remove this hack.

fpga/Makefile

@@ -38,7 +38,7 @@ PREREQFILES = $(mifdir)/sram.mif \
 alltarg := sof pof jic svf svf.gz xsvf xsvf.gz rbf rbf.gz \
 	   rpd rpd.gz pow.rpt sta.rpt
 allout   = $(foreach o,$(alltarg),$(outdir)/$(1).$(o))
-vartarg := mif_update.rpt sof svf svf.gz rbf rbf.gz
+vartarg := sof svf svf.gz rbf rbf.gz
 varout   = $(foreach o,$(vartarg),$(outdir)/$(1).$(o))
 
 sram_src = ../rv32/