x86 setup: drop SWAP_DEV

Impact: None (cleanup)

SWAP_DEV is unused since 2.6.23-rc1. The comment was already incorrect
since (at least) 2.6.12.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/boot/header.S

@@ -30,7 +30,6 @@ SYSSEG		= DEF_SYSSEG		/* system loaded at 0x10000 (65536) */
 SYSSIZE		= DEF_SYSSIZE		/* system size: # of 16-byte clicks */
 					/* to be loaded */
 ROOT_DEV	= 0			/* ROOT_DEV is now written by "build" */
-SWAP_DEV	= 0			/* SWAP_DEV is now written by "build" */
 
 #ifndef SVGA_MODE
 #define SVGA_MODE ASK_VGA