target-*: dfilter support for in_asm

The arm target was handled by 06486077, but other targets
were ignored.  This handles all the rest which actually support
disassembly (that is, skipping moxie and tilegx).

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>