x86, setup: Rename BOOT_ISDIGIT_H to BOOT_CTYPE_H

arch/x86/boot/isdigit.h was renamed to arch/x86/boot/ctype.h in
6238b47b

 ("x86, setup: move isdigit.h to ctype.h, header files on top.")
Adjust guards too.

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Link: http://lkml.kernel.org/r/1420267941-26390-1-git-send-email-kuleshovmail@gmail.com


Signed-off-by: Borislav Petkov <bp@suse.de>