xtensa: reading privileged special registers

[Max Filippov]

> Please, help us to precisely identify what exactly do you experience
> by answering some questions:
> 1) Did you apply a source overlay for your specific hardware ?

Yes, I have applied publicly available dc232b overlay. Although the
code that returns zeros for privileged SRs is not overlay-specific.

> 2) What Xtensa processor do you work with ( if it's not a secret ) ?
>     What privileged registers do you have problems with ?

It is not a processor, it is qemu-based ISS that I've been developing.
It emulates dc232b.
I was mostly interested in $ccount/$ccompare.
I started to dig here because although I've implemented access to
these registers in gdbstub, I couldn't make gdb to query them.

-- 
Thanks.
-- Max