radeonsi: parse and dump status registers on GPU hang

radeonsi: parse and dump status registers on GPU hang

GPU hang detection must be enabled by setting: GALLIUM_DDEBUG=[timeout in ms]

This may print too much information that we might not understand yet,
but some of the bits are very useful.

Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>