powerpc/cacheflush: fix variable set but not used

The powerpc's flush_cache_vmap() is defined as a macro and never use
both of its arguments, so it will generate a compilation warning,

lib/ioremap.c: In function 'ioremap_page_range':
lib/ioremap.c:203:16: warning: variable 'start' set but not used
[-Wunused-but-set-variable]

Fix it by making it an inline function.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/cacheflush.h

@@ -32,9 +32,12 @@
  * not expect this type of fault. flush_cache_vmap is not exactly the right
  * place to put this, but it seems to work well enough.
  */
-#define flush_cache_vmap(start, end)		do { asm volatile("ptesync" ::: "memory"); } while (0)
+static inline void flush_cache_vmap(unsigned long start, unsigned long end)
+{
+	asm volatile("ptesync" ::: "memory");
+}
 #else
-#define flush_cache_vmap(start, end)		do { } while (0)
+static inline void flush_cache_vmap(unsigned long start, unsigned long end) { }
 #endif
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1