xen: fix p2m section mismatches

Fix section mismatch warnings:
set_phys_range_identity() is called by __init xen_set_identity(),
so also mark set_phys_range_identity() as __init.
then:
__early_alloc_p2m() is called set_phys_range_identity(), so also mark
__early_alloc_p2m() as __init.

WARNING: arch/x86/built-in.o(.text+0x7856): Section mismatch in reference from the function __early_alloc_p2m() to the function .init.text:extend_brk()
The function __early_alloc_p2m() references
the function __init extend_brk().
This is often because __early_alloc_p2m lacks a __init
annotation or the annotation of extend_brk is wrong.

WARNING: arch/x86/built-in.o(.text+0x7967): Section mismatch in reference from the function set_phys_range_identity() to the function .init.text:extend_brk()
The function set_phys_range_identity() references
the function __init extend_brk().
This is often because set_phys_range_identity lacks a __init
annotation or the annotation of extend_brk is wrong.

[v2: Per Stephen Hemming recommonedation made __early_alloc_p2m static]
Signed-off-by: Randy Dunlap <[e-mail]>
Signed-off-by: Konrad Rzeszutek Wilk <[e-mail]>

arch/x86/xen/p2m.c

···
 	return true;
 }
 
-bool __early_alloc_p2m(unsigned long pfn)
+static bool __init __early_alloc_p2m(unsigned long pfn)
 {
 	unsigned topidx, mididx, idx;
 
···
 	}
 	return idx != 0;
 }
-unsigned long set_phys_range_identity(unsigned long pfn_s,
+unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 				      unsigned long pfn_e)
 {
 	unsigned long pfn;