x86: fix usage of bios intcall()

Some intcall() misuses the input biosregs as output in
cf06de7b9cdd3efee7a59dced1977b3c21d43732

This fixes the problem vga=ask boot option doesn't show enough modes.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
LKML-Reference: <20090701021307.GA3127@localhost.localdomain>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
index c700147..275dd17 100644
--- a/arch/x86/boot/video-vesa.c
+++ b/arch/x86/boot/video-vesa.c
@@ -45,7 +45,7 @@
 	ireg.di = (size_t)&vginfo;
 	intcall(0x10, &ireg, &oreg);
 
-	if (ireg.ax != 0x004f ||
+	if (oreg.ax != 0x004f ||
 	    vginfo.signature != VESA_MAGIC ||
 	    vginfo.version < 0x0102)
 		return 0;	/* Not present */
@@ -70,7 +70,7 @@
 		ireg.di = (size_t)&vminfo;
 		intcall(0x10, &ireg, &oreg);
 
-		if (ireg.ax != 0x004f)
+		if (oreg.ax != 0x004f)
 			continue;
 
 		if ((vminfo.mode_attr & 0x15) == 0x05) {