nb/intel/haswell: Use PCI bitwise ops

Tested with BUILD_TIMELESS=1, Asrock B85M Pro4 does not change.

Change-Id: I99379299f7e744a3e906bdbc46d55060d9c75d6a
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42153
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/haswell/early_init.c b/src/northbridge/intel/haswell/early_init.c
index fb148fa..fd188a1 100644
--- a/src/northbridge/intel/haswell/early_init.c
+++ b/src/northbridge/intel/haswell/early_init.c
@@ -37,7 +37,6 @@
 {
 	bool igd_enabled;
 	u16 ggc;
-	u8 reg8;
 
 	printk(BIOS_DEBUG, "Initializing IGD...\n");
 
@@ -59,10 +58,7 @@
 	}
 
 	/* Enable 256MB aperture */
-	reg8 = pci_read_config8(PCI_DEV(0, 2, 0), MSAC);
-	reg8 &= ~0x06;
-	reg8 |= 0x02;
-	pci_write_config8(PCI_DEV(0, 2, 0), MSAC, reg8);
+	pci_update_config8(PCI_DEV(0, 2, 0), MSAC, ~0x06, 0x02);
 }
 
 static void start_peg2_link_training(const pci_devfn_t dev)