soc/intel/apollolake: Make use of is_devfn_enabled() function

1. Replace all pcidev_path_on_root() and is_dev_enabled() functions
combination with is_devfn_enabled().
2. Remove unused local variable of device structure type
(struct device *).
3. Replace pcidev_path_on_root() and dev->enabled check with
is_devfn_enabled() call.

TEST=Able to build and boot without any regression seen on Reef.

Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Change-Id: I900038dd4b2e2d89b1236bbd26bec5f34483b9f3
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55327
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/soc/intel/apollolake/acpi.c b/src/soc/intel/apollolake/acpi.c
index 34f760f..ae20245 100644
--- a/src/soc/intel/apollolake/acpi.c
+++ b/src/soc/intel/apollolake/acpi.c
@@ -143,7 +143,6 @@
 
 static unsigned long soc_fill_dmar(unsigned long current)
 {
-	struct device *const igfx_dev = pcidev_path_on_root(SA_DEVFN_IGD);
 	uint64_t gfxvtbar = MCHBAR64(GFXVTBAR) & VTBAR_MASK;
 	uint64_t defvtbar = MCHBAR64(DEFVTBAR) & VTBAR_MASK;
 	bool gfxvten = MCHBAR32(GFXVTBAR) & VTBAR_ENABLED;
@@ -151,7 +150,7 @@
 	unsigned long tmp;
 
 	/* IGD has to be enabled, GFXVTBAR set and enabled. */
-	const bool emit_igd = is_dev_enabled(igfx_dev) && gfxvtbar && gfxvten;
+	const bool emit_igd = is_devfn_enabled(SA_DEVFN_IGD) && gfxvtbar && gfxvten;
 
 	/* First, add DRHD entries */
 	if (emit_igd) {