drm/i915: Remove unused BSM_MASK causing warning

Remove never used BSM{,_MASK}. BSM_MASK #define also causes a warning.

include/drm/i915_drm.h:96:34: warning: result of ‘65535 << 20’
requires 37 bits to represent, but ‘int’ only has 32 bits
[-Wshiftoverflow=]
   #define   INTEL_BSM_MASK (0xFFFF << 20)
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1476256734-6457-1-git-send-email-joonas.lahtinen@linux.intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -86,8 +86,7 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define DEVEN 0x54
 #define   DEVEN_MCHBAR_EN (1 << 28)
 
-#define BSM 0x5c
-#define   BSM_MASK (0xFFFF << 20)
+/* BSM in include/drm/i915_drm.h */
 
 #define HPLLCC	0xc0 /* 85x only */
 #define   GC_CLOCK_CONTROL_MASK		(0x7 << 0)