[PATCH] drm/i915/gmch: fix build error var set but not used

[Wang Jinchao <wangjinchao@xfusion.com>]

When CONFIG_PNP is not defined, i915 will fail to compile with error bellow:
	drivers/gpu/drm/i915/soc/intel_gmch.c:43:13: error: variable ‘mchbar_addr’ set but not used
Fix it by surrounding variable declaration and assignment with ifdef

Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
---
 drivers/gpu/drm/i915/soc/intel_gmch.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/soc/intel_gmch.c b/drivers/gpu/drm/i915/soc/intel_gmch.c
index 6d0204942f7a..d2c442b0b4eb 100644
--- a/drivers/gpu/drm/i915/soc/intel_gmch.c
+++ b/drivers/gpu/drm/i915/soc/intel_gmch.c
@@ -38,16 +38,17 @@ intel_alloc_mchbar_resource(struct drm_i915_private *i915)
 {
 	int reg = GRAPHICS_VER(i915) >= 4 ? MCHBAR_I965 : MCHBAR_I915;
 	u32 temp_lo, temp_hi = 0;
-	u64 mchbar_addr;
 	int ret;
-
+#ifdef CONFIG_PNP
+	u64 mchbar_addr;
+#endif
 	if (GRAPHICS_VER(i915) >= 4)
 		pci_read_config_dword(i915->gmch.pdev, reg + 4, &temp_hi);
 	pci_read_config_dword(i915->gmch.pdev, reg, &temp_lo);
-	mchbar_addr = ((u64)temp_hi << 32) | temp_lo;
 
 	/* If ACPI doesn't have it, assume we need to allocate it ourselves */
 #ifdef CONFIG_PNP
+	mchbar_addr = ((u64)temp_hi << 32) | temp_lo;
 	if (mchbar_addr &&
 	    pnp_range_reserved(mchbar_addr, mchbar_addr + MCHBAR_SIZE))
 		return 0;
-- 
2.40.0