x86, boot: Remove obsolete and unused constant RAMDISK

The named constant RAMDISK is unused. It used to set the (obsolete)
kernel boot header field ram_size, but its usage for that purpose got
dropped in commit 5e47c478 ("x86: remove
zImage support"). Now remove this constant too.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Link: http://lkml.kernel.org/r/1345396003.1771.9.camel@x61.thuisdomeinSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/boot/header.S

@@ -32,10 +32,6 @@ SYSSEG		= 0x1000		/* historical load address >> 4 */
 #define SVGA_MODE ASK_VGA
 #endif
 
-#ifndef RAMDISK
-#define RAMDISK 0
-#endif
-
 #ifndef ROOT_RDONLY
 #define ROOT_RDONLY 1
 #endif