drm/i915/lrc: Update reg_state macros to pass checkpatch

drm/i915/lrc: Update reg_state macros to pass checkpatch

The macros we use to init the reg_state had the following issues reported
by checkpatch --strict.

  Macro argument reuse 'reg_state' - possible side-effects
  Macro argument reuse 'pos' - possible side-effects
  Macro argument reuse 'ppgtt' - possible side-effects
  spaces preferred around that '+' (ctx:VxV)

So fix these issues before they are moved to a new header file.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180124004349.22126-1-michel.thierry@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>