drm/radeon: add hard_reset module parameter

Enabling this parameter enables pci config reset,
aka hard reset, which is a bus level chip reset.
In some cases this works more reliably than a soft
reset.  Disabled by default.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/radeon.h
Simple merge

diff --cc drivers/gpu/drm/radeon/radeon_drv.c
Simple merge