drm/i915/uc: Unify uC firmware upload

The way we load the firmwares is the same for both GuC and HuC, the only
difference is in the wopcm destination address and the dma flags, so we
easily can move the logic to a common function and pass in offset and
flags. The only other difference in the uplaod path are some the extra
steps that guc does before and after the xfer, but those don't require
the guc fw to be pinned in ggtt and can safely be performed before
calling the uc_upload function.

Note that this patch re-introduces the dma xfer wait for guc loading that
was removed with "drm/i915/guc: Propagate the fw xfer timeout". This is
not going to slow us down on a successful load (the dma has to complete
before fw init can start), but could slightly increase the timeout in case
of a fw init error.

v2: use _fw variants for uncore accesses (Chris), fix guc_fw status on
    failed wait.

v3: use dev_err and print DMA_CTRL (Chris)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190725001813.4740-9-daniele.ceraolospurio@intel.com