drm/i915: Convert to BITS_PER_TYPE

In commit 9144d75e22ca ("include/linux/bitops.h: introduce BITS_PER_TYPE"),
we made BITS_PER_TYPE available to all and now we can use the macro to
replace some open-coded computation of sizeof(T) * BITS_PER_BYTE.

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180926104707.17410-1-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 44e2c0f..ade9bca 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1649,8 +1649,8 @@ i915_driver_create(struct pci_dev *pdev, const struct pci_device_id *ent)
 	device_info->device_id = pdev->device;
 
 	BUILD_BUG_ON(INTEL_MAX_PLATFORMS >
-		     sizeof(device_info->platform_mask) * BITS_PER_BYTE);
-	BUG_ON(device_info->gen > sizeof(device_info->gen_mask) * BITS_PER_BYTE);
+		     BITS_PER_TYPE(device_info->platform_mask));
+	BUG_ON(device_info->gen > BITS_PER_TYPE(device_info->gen_mask));
 
 	return i915;
 }