drm/i915: Kill GEN_FOREVER

commit ac657f6461 ("drm/i915: Introduce IS_GEN macro") introduced
GEN_FOREVER that was never used.

My first attempt was to rename it to FOREVER since GEN is
already part of the macro. Then I used coccinelle to change all
-INTEL_GEN(e1) >= e2
+INTEL_GEN_RANGE(e1, e2, FOREVER)
-INTEL_GEN(e1) <= e2
+INTEL_GEN_RANGE(e1, 0, e2)

and I liked it.

However I didn't like very much the remaining
INTEL_GEN(dev_priv) < n

and:
INTEL_GEN(e1) < n
INTEL_GEN_RANGE(e1, 0, n - 1)

didn't make much sense either.

So INTEL_GEN use for > or < seems a better unified way for unlimited
bounds. So, no reason to keep GEN_FOREVER here.

Let's kill before someone start using it.

v2: Remove remaining GEN_FOREVER forgotten in a comment. (Daniel)

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181026195143.20353-2-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -2355,20 +2355,12 @@ intel_info(const struct drm_i915_private *dev_priv)
 #define REVID_FOREVER		0xff
 #define INTEL_REVID(dev_priv)	((dev_priv)->drm.pdev->revision)
 
-#define GEN_FOREVER (0)
-
 #define INTEL_GEN_MASK(s, e) ( \
 	BUILD_BUG_ON_ZERO(!__builtin_constant_p(s)) + \
 	BUILD_BUG_ON_ZERO(!__builtin_constant_p(e)) + \
-	GENMASK((e) != GEN_FOREVER ? (e) - 1 : BITS_PER_LONG - 1, \
-		(s) != GEN_FOREVER ? (s) - 1 : 0) \
-)
+	GENMASK((e) - 1, (s) - 1))
 
-/*
- * Returns true if Gen is in inclusive range [Start, End].
- *
- * Use GEN_FOREVER for unbound start and or end.
- */
+/* Returns true if Gen is in inclusive range [Start, End] */
 #define IS_GEN(dev_priv, s, e) \
 	(!!((dev_priv)->info.gen_mask & INTEL_GEN_MASK((s), (e))))