xen/riscv: move extern of cpu0_boot_stack to header

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

xen/arch/riscv/include/asm/mm.h

@@ -8,6 +8,8 @@
 #define pfn_to_paddr(pfn) ((paddr_t)(pfn) << PAGE_SHIFT)
 #define paddr_to_pfn(pa)  ((unsigned long)((pa) >> PAGE_SHIFT))
 
+extern unsigned char cpu0_boot_stack[];
+
 void setup_initial_pagetables(void);
 
 void enable_mmu(void);

xen/arch/riscv/mm.c

@@ -19,8 +19,6 @@ struct mmu_desc {
     pte_t *pgtbl_base;
 };
 
-extern unsigned char cpu0_boot_stack[STACK_SIZE];
-
 #define PHYS_OFFSET ((unsigned long)_start - XEN_VIRT_START)
 #define LOAD_TO_LINK(addr) ((addr) - PHYS_OFFSET)
 #define LINK_TO_LOAD(addr) ((addr) + PHYS_OFFSET)