The problem is that this causes writes to registers, and if the pipe
is off they might go nowhere (e.g. when runtime pm is enabled).
Furthermore we can only really check once the modeset setup is done,
but again most tests set up the CRC structure before calling
igt_commit and friends. We could add crc restore support to the
kernel's rpm code, but that will end up being rather invasive and
fragile hard-to-test code.

Now originally this was needed back when CRC support wasn't available
everywhere. But that's fixed now.

So given all this just drop that sanity check and make sure that we
only touch the debugfs file (and so the hw state) when we know the
pipe is running in the desired configuration.

A complementary kernel patch will try to catch offenders by returning
-EIO if the pipe is off.

v2: Forgot to git add one hunk.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86092


Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>