drm/i915: Add global forcewake request to drpc

We have seen multiple RC6 issues where it is useful to know
which global forcewake bits are set. Add this to the 'drpc'
debugfs output.

v2: Review comments (Ashutosh)

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220617212032.34577-1-vinay.belgaumkar@intel.com