x86/setup: Ignore early boot parameters like no-real-mode

x86/setup: Ignore early boot parameters like no-real-mode

There are parameters in xen/arch/x86/boot/cmdline.c that
are only used early in the boot process, so handlers are
necessary to avoid an "Unknown command line option" in
dmesg.

This also updates ignore_param() to generate a temporary
variable name so that the macro can be used more than once
per file.

Signed-off-by: Trammell hudson <hudson@trmm.net>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
[Leave note to stop TEMP_NAME() finding more general use]
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>