lib/bootconfig: Make xbc_alloc_mem() and xbc_free_mem() as __init function

lib/bootconfig: Make xbc_alloc_mem() and xbc_free_mem() as __init function

Since the xbc_alloc_mem() and xbc_free_mem() are used from
the __init functions and memblock_alloc() is __init function,
make them __init functions too.

Link: https://lkml.kernel.org/r/163515075747.547467.5746167540626712819.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: c7d94c12fe79 ("bootconfig: Cleanup dummy headers in tools/bootconfig")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>