openrisc: drop wrongly typed definition of page_to_virt()

To align with generic code and other architectures that expect the macro
page_to_virt to produce an expression whose type is 'void*', drop the
arch specific definition, which is never referenced anyway.
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/openrisc/include/asm/page.h

@@ -81,8 +81,6 @@ typedef struct page *pgtable_t;
 
 #define virt_to_page(addr) \
 	(mem_map + (((unsigned long)(addr)-PAGE_OFFSET) >> PAGE_SHIFT))
-#define page_to_virt(page) \
-	((((page) - mem_map) << PAGE_SHIFT) + PAGE_OFFSET)
 
 #define page_to_phys(page)      ((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)