Add secure boot support for the GM20B chip found in Tegra X1. Secure
boot on Tegra works slightly differently from desktop, notably in the
way the WPR region is set up.

In addition, the firmware bootloaders use a slightly different header
format.
Signed-off-by: NAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

Add secure-boot for the dGPU set of GM20X chips, using the PMU as the
high-secure falcon.

This work is based on Deepak Goyal's initial port of Secure Boot to
Nouveau.

v2. use proper memory target function
Signed-off-by: NAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

On GM200 and later GPUs, firmware for some essential falcons (notably
GR ones) must be authenticated by a NVIDIA-produced signature and
loaded by a high-secure falcon in order to be able to access privileged
registers, in a process known as Secure Boot.

Secure Boot requires building a binary blob containing the firmwares
and signatures of the falcons to be loaded. This blob is then given to
a high-secure falcon running a signed loader firmware that copies the
blob into a write-protected region, checks that the signatures are
valid, and finally loads the verified firmware into the managed falcons
and switches them to privileged mode.

This patch adds infrastructure code to support this process on chips
that require it.

v2:
- The IRQ mask of the PMU falcon was left - replace it with the proper
  irq_mask variable.
- The falcon reset procedure expecting a falcon in an initialized state,
  which was accidentally provided by the PMU subdev. Make sure that
  secboot can manage the falcon on its own.
Signed-off-by: NAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>