RISC-V: Make our port sparse-clean

This patch set contains a handful of fixes that clean up the sparse
results for the RISC-V port.  These patches shouldn't have any
functional difference.  The patches:

* Use NULL instead of 0.
* Clean up __user annotations.
* Split __copy_user into two functions, to make the __user annotations
  valid.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

arch/riscv/include/asm/cacheflush.h

@@ -47,7 +47,7 @@ static inline void flush_dcache_page(struct page *page)
 
 #else /* CONFIG_SMP */
 
-#define flush_icache_all() sbi_remote_fence_i(0)
+#define flush_icache_all() sbi_remote_fence_i(NULL)
 void flush_icache_mm(struct mm_struct *mm, bool local);
 
 #endif /* CONFIG_SMP */

arch/riscv/include/asm/tlbflush.h

@@ -49,7 +49,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
 
 #include <asm/sbi.h>
 
-#define flush_tlb_all() sbi_remote_sfence_vma(0, 0, -1)
+#define flush_tlb_all() sbi_remote_sfence_vma(NULL, 0, -1)
 #define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, 0)
 #define flush_tlb_range(vma, start, end) \
 	sbi_remote_sfence_vma(mm_cpumask((vma)->vm_mm)->bits, \

arch/riscv/include/asm/uaccess.h

@@ -392,19 +392,21 @@ do {								\
 })
 
 
-extern unsigned long __must_check __copy_user(void __user *to,
+extern unsigned long __must_check __asm_copy_to_user(void __user *to,
+	const void *from, unsigned long n);
+extern unsigned long __must_check __asm_copy_from_user(void *to,
 	const void __user *from, unsigned long n);
 
 static inline unsigned long
 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	return __copy_user(to, from, n);
+	return __asm_copy_to_user(to, from, n);
 }
 
 static inline unsigned long
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	return __copy_user(to, from, n);
+	return __asm_copy_from_user(to, from, n);
 }
 
 extern long strncpy_from_user(char *dest, const char __user *src, long count);