arch: Get rid of global maximums for numbers of source/dest/misc regs.

Change-Id: I6881572daedf0f0e9ff6aee4f174671d02ef743d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38389
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>

src/arch/SConscript

@@ -185,8 +185,6 @@ def ISADesc(desc, decoder_splits=1, exec_splits=1):
     add_gen('exec-g.cc.inc')
     add_gen('exec-ns.cc.inc')
 
-    add_gen('max_inst_regs.hh')
-
 
     # These generated files are also top level sources.
     def source_gen(name):