unicore32: EXPORT_SYMBOL needs export.h

Include export.h to fix below warning:

CC arch/unicore32/mm/init.o
arch/unicore32/mm/init.c:227: warning: data definition has no type or storage class
arch/unicore32/mm/init.c:227: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
arch/unicore32/mm/init.c:227: warning: parameter names (without types) in function declaration

Signed-off-by: Axel Lin <[e-mail]>
Signed-off-by: Paul Gortmaker <[e-mail]>

arch/unicore32/mm/init.c

···
 #include <linux/memblock.h>
 #include <linux/sort.h>
 #include <linux/dma-mapping.h>
+#include <linux/export.h>
 
 #include <asm/sections.h>
 #include <asm/setup.h>