ARC: mm: HIGHMEM: Fix section mismatch splat

| WARNING: vmlinux.o(.text+0xd6c2): Section mismatch in reference from the function alloc_kmap_pgtable() to the function
| .init.text:__alloc_bootmem_low()
The function alloc_kmap_pgtable() references the function __init __alloc_bootmem_low().
This is often because alloc_kmap_pgtable lacks a __init annotation or the annotation of __alloc_bootmem_low is wrong.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

arch/arc/mm/highmem.c

@@ -111,7 +111,7 @@ void __kunmap_atomic(void *kv)
 }
 EXPORT_SYMBOL(__kunmap_atomic);
 
-noinline pte_t *alloc_kmap_pgtable(unsigned long kvaddr)
+static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr)
 {
 	pgd_t *pgd_k;
 	pud_t *pud_k;
@@ -127,7 +127,7 @@ noinline pte_t *alloc_kmap_pgtable(unsigned long kvaddr)
 	return pte_k;
 }
 
-void kmap_init(void)
+void __init kmap_init(void)
 {
 	/* Due to recursive include hell, we can't do this in processor.h */
 	BUILD_BUG_ON(PAGE_OFFSET < (VMALLOC_END + FIXMAP_SIZE + PKMAP_SIZE));