drm/i915: Don't require dev->struct_mutex in psr_match_conditions

Since I've reworked psr support to no longer require x-tiling we don't
check any state protected by the Giant GEM Lock. So drop that check.

Also boo for lockdep_assert_held for not yelling when lockdep is
disabled.

Cc: Paulo Zanoni <przanoni@gmail.com>
Reported-by: Paulo Zanoni <przanoni@gmail.com>
Acked-by: Paulo Zanoni <przanoni@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>