Before lane reversal,
De-asserts STRAP_BIF_all_valid for
PCIE-GFX core.
After lane reversal,
Asserts STRAP_BIF_all_valid for
PCIE-GFX core.

Signed-off-by: Zheng Bao <zheng.bao@amd.com>

Index: src/southbridge/amd/rs780/rs780_gfx.c
===================================================================
--- src/southbridge/amd/rs780/rs780_gfx.c	(revision 6137)
+++ src/southbridge/amd/rs780/rs780_gfx.c	(working copy)
@@ -1302,8 +1302,10 @@
 		if(is_dev3_present()){
 			/* step 1, lane reversal (only need if CMOS option is enabled) */
 			if (cfg->gfx_lane_reversal) {
+				set_nbmisc_enable_bits(nb_dev, 0x36, 1 << 31, 1 << 31);
 				set_nbmisc_enable_bits(nb_dev, 0x33, 1 << 2, 1 << 2);
 				set_nbmisc_enable_bits(nb_dev, 0x33, 1 << 3, 1 << 3);
+				set_nbmisc_enable_bits(nb_dev, 0x36, 1 << 31, 0 << 31);
 			}
 			printk(BIOS_DEBUG, "rs780_gfx_init step1.\n");
 			/* step 1.1, dual-slot gfx configuration (only need if CMOS option is enabled) */
@@ -1317,10 +1319,11 @@
 
 		}else{
 			if (cfg->gfx_lane_reversal) {
+				set_nbmisc_enable_bits(nb_dev, 0x36, 1 << 31, 1 << 31);
 				set_nbmisc_enable_bits(nb_dev, 0x33, 1 << 2, 1 << 2);
+				set_nbmisc_enable_bits(nb_dev, 0x36, 1 << 31, 0 << 31);
 			}
 			printk(BIOS_DEBUG, "rs780_gfx_init step1.\n");
-			printk(BIOS_DEBUG, "rs780_gfx_init step2.\n");
 
 			if((dev->path.pci.devfn >> 3) == 2)
 				single_port_configuration(nb_dev, dev);