LDSCRIPT: Name INIT_RAM_FS consistently

In asm-generic/vmlinux.lds.h, name INIT_RAM_FS consistently, no matter the
setting of CONFIG_BLK_DEV_INITRD.  This corrects:

	commit ef53dae8
	Author: Sam Ravnborg <sam@ravnborg.org>
	Date:   Sun Jun 7 20:46:37 2009 +0200
	Subject: Improve vmlinux.lds.h support for arch specific linker scripts

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>