sim: bfin: drop RET[ENI] setup

sim: bfin: drop RET[ENI] setup

Since these insns run in usermode, there should be no need to setup
RET[ENI] to safe values.  They won't be dereferenced, and any insn
that returns via them are valid only in supervisor mode.  Since this
is in the main exception code path, saving any insn at all is good
as it gets multiplied quickly (as in O(n^2) times).

Signed-off-by: Mike Frysinger <vapier@gentoo.org>