drm/i915: Reduce trickery in DEV_INFO_FOR_EACH_FLAG

Get rid of SEP_SEMICOLON and SEP_BLANK in DEV_INFO_FOR_EACH_FLAG.
Consolidate the debug output so that instead of one huge line with
"cap1,cap2,capN" each capability is split to own line and displayed
as "capN: [yes|no]" to make the dumps more historically informative.

v2:
- Do not break auto-indent by keeping semicolon after macro (Jani)
- Consolidate and use yesno() in all locations (Chris)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>