gfx: pvr: add hwrec_debugfs entries

gfx: pvr: add hwrec_debugfs entries

These entries provide details about an SGX HW recovery event. In general
the hwrec_xxx entry will provide a snapshot of the corresponding state
as it was at the time of the last recovery, while the xxx entry will
give the current state.

At the moment we have hwrec_event and hwrec_sgx_registers. hwrec_event
is special in that it can be used to step to the next HW recovery event.
After it's opened and read all other hwrec_* entries will provide the
state for the same event. A second open on hwrec_event will reset all
hwrec_* entries, in preparation for the next event.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>