x86: fix the missing BIOS area check in page_is_ram

page_is_ram has a FIXME since ages, which reminds to sanity check the
BIOS area between 640k and 1M, which is sometimes falsely reported as
RAM in the e820 tables.

Implement the sanity check. Move the BIOS range defines from
pageattr.c into e820.h to avoid duplicate defines.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/e820.h b/include/asm-x86/e820.h
index f96f185..7004251 100644
--- a/include/asm-x86/e820.h
+++ b/include/asm-x86/e820.h
@@ -25,6 +25,9 @@
 #define ISA_START_ADDRESS	0xa0000
 #define ISA_END_ADDRESS		0x100000
 
+#define BIOS_BEGIN		0x000a0000
+#define BIOS_END		0x00100000
+
 #ifdef __KERNEL__
 #ifdef CONFIG_X86_32
 # include "e820_32.h"