riscv: Fix implicit declaration of 'page_to_section'

With CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP,

arch/riscv/include/asm/pgtable.h: In function ‘mk_pte’:
include/asm-generic/memory_model.h:64:14: error: implicit declaration of function ‘page_to_section’; did you mean ‘present_section’? [-Werror=implicit-function-declaration]
  int __sec = page_to_section(__pg);   \
              ^~~~~~~~~~~~~~~

Fixed by changing mk_pte() from inline function to macro.

Cc: Logan Gunthorpe <logang@deltatee.com>
Fixes: d95f1a54 ("RISC-V: Implement sparsemem")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
[paul.walmsley@sifive.com: fixed checkpatch errors]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/include/asm/pgtable.h

@@ -184,10 +184,7 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t prot)
 	return __pte((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
 }
 
-static inline pte_t mk_pte(struct page *page, pgprot_t prot)
-{
-	return pfn_pte(page_to_pfn(page), prot);
-}
+#define mk_pte(page, prot)       pfn_pte(page_to_pfn(page), prot)
 
 #define pte_index(addr) (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))