i#1551 port to ARM: fix wrong ISA mode on updating gencode
i#1551 port to ARM: fix wrong ISA mode on updating gencode

When we update the IBl gencode we need to swap back to the default ISA
mode.

Review-URL: https://codereview.appspot.com/202400043

bl4ckic3/dynamorio,sigma-random/dynamorio,sigma-random/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio,daksunt/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,daksunt/dynamorio,code4bones/dynamorio,code4bones/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,sigma-random/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio