mdspr2 add to gcc 4.2.1

From: Mori Hiroki <yamori813_at_yahoo.co.jp>
Date: Tue, 09 Aug 2022 07:18:54 UTC
Hi.

I add 4.3 mdspr2 support to 4.2.1.

https://github.com/ZRouter/freebsd-src/tree/yamori813_modify

also enable to mx status bit on process used by dsp instruction.

I tested qeum test code on Atheros 74K. That is work fine.

save and load is not yet.

Dose some body write dsp code for mpg123 ?

Regards

Hiroki Mori