Many Hexagon python scripts call hex_common.get_tagregs(), but only one
call site use the full reg structure given by this function. To make the
code cleaner, let's make get_tagregs() filter out the unused fields
(i.e. 'toss' and 'numregs'), properly removed the unused variables at
the call sites. The hex_common.bad_register() function is also adjusted
to work exclusively with 'regtype' and 'regid' args. For the single call
site that does use toss/numregs, we provide an optional parameter to
get_tagregs() which will restore the old full behavior.

Suggested-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Tested-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <3ffd4ccb972879f57f499705c624e8eaba7f8b52.1684939078.git.quic_mathbern@quicinc.com>