platform/x86: dell-smbios: Prefix class/select with cmd_

Later on these structures will be brought up to userspace.
the word "class" is a reserved word in c++ and this will prevent
uapi headers from being included directly in c++ programs.

To make life easier on these applications, prepare the change now.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>