ARC: hide unused function unw_hdr_alloc

As kernelci.org reports, this function is not used in
vdk_hs38_defconfig:

arch/arc/kernel/unwind.c:188:14: warning: 'unw_hdr_alloc' defined but not used [-Wunused-function]

Fixes: bc79c9a721 ("ARC: dw2 unwind: Reinstante unwinding out of modules")
Link: https://kernelci.org/build/id/5d1cae3f59b514300340c132/logs/
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/unwind.c

@@ -181,11 +181,6 @@ static void *__init unw_hdr_alloc_early(unsigned long sz)
 	return memblock_alloc_from(sz, sizeof(unsigned int), MAX_DMA_ADDRESS);
 }
 
-static void *unw_hdr_alloc(unsigned long sz)
-{
-	return kmalloc(sz, GFP_KERNEL);
-}
-
 static void init_unwind_table(struct unwind_table *table, const char *name,
 			      const void *core_start, unsigned long core_size,
 			      const void *init_start, unsigned long init_size,
@@ -366,6 +361,10 @@ ret_err:
 }
 
 #ifdef CONFIG_MODULES
+static void *unw_hdr_alloc(unsigned long sz)
+{
+	return kmalloc(sz, GFP_KERNEL);
+}
 
 static struct unwind_table *last_table;