drm/i915/gt: Wrap macro arg in ()

Checkpatch noticed that ppgtt->pd should have been (ppgtt)->pd to avoid
issues with macros.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210122192913.4518-6-chris@chris-wilson.co.ukSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/gt/intel_lrc_reg.h

@@ -39,7 +39,7 @@
 
 #define ASSIGN_CTX_PML4(ppgtt, reg_state) do { \
 	u32 *reg_state__ = (reg_state); \
-	const u64 addr__ = px_dma(ppgtt->pd); \
+	const u64 addr__ = px_dma((ppgtt)->pd); \
 	(reg_state__)[CTX_PDP0_UDW] = upper_32_bits(addr__); \
 	(reg_state__)[CTX_PDP0_LDW] = lower_32_bits(addr__); \
 } while (0)