drm/i915: extract intel_uncore_trace.[ch]

The i915_reg_rw tracing is a small isolated part of i915_trace.h. Its
users are orthogonal to the other i915_trace.h users as well, and its
implementation does not require all the includes of i915_trace.h. Split
i915_reg_rw tracing to separate intel_uncore_trace.[ch].

The main underlying goal is to reduce implicit includes of i915_drv.h
from display code.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1a3623fbb120adc55bc1cab1e27aca6e55487163.1732104170.git.jani.nikula@intel.com