MIPS: Silence missing prototype warning

Silence the following two warnings when make W=1:

  CC      arch/mips/lib/bswapsi.o
arch/mips/lib/bswapsi.c:5:22: warning: no previous prototype for '__bswapsi2' [-Wmissing-prototypes]
 unsigned int notrace __bswapsi2(unsigned int u)
                      ^~~~~~~~~~
  CC      arch/mips/lib/bswapdi.o
arch/mips/lib/bswapdi.c:5:28: warning: no previous prototype for '__bswapdi2' [-Wmissing-prototypes]
 unsigned long long notrace __bswapdi2(unsigned long long u)
                            ^~~~~~~~~~
  AR      arch/mips/lib/built-in.a

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: seehearfeel

arch/mips/lib/bswapdi.c

@@ -2,6 +2,9 @@
 #include <linux/export.h>
 #include <linux/compiler.h>
 
+/* To silence -Wmissing-prototypes. */
+unsigned long long __bswapdi2(unsigned long long u);
+
 unsigned long long notrace __bswapdi2(unsigned long long u)
 {
 	return (((u) & 0xff00000000000000ull) >> 56) |
@@ -13,5 +16,4 @@ unsigned long long notrace __bswapdi2(unsigned long long u)
 	       (((u) & 0x000000000000ff00ull) << 40) |
 	       (((u) & 0x00000000000000ffull) << 56);
 }
-
 EXPORT_SYMBOL(__bswapdi2);

arch/mips/lib/bswapsi.c

@@ -2,12 +2,14 @@
 #include <linux/export.h>
 #include <linux/compiler.h>
 
+/* To silence -Wmissing-prototypes. */
+unsigned int __bswapsi2(unsigned int u);
+
 unsigned int notrace __bswapsi2(unsigned int u)
 {
 	return (((u) & 0xff000000) >> 24) |
 	       (((u) & 0x00ff0000) >>  8) |
 	       (((u) & 0x0000ff00) <<  8) |
 	       (((u) & 0x000000ff) << 24);
 }
-
 EXPORT_SYMBOL(__bswapsi2);