powerpc: Force cast on memcpy_toio()

sparse reports the following warning:

  CHECK   arch/powerpc/cpu/mpc8xx/micropatch_usb_sof.c
arch/powerpc/cpu/mpc8xx/micropatch_usb_sof.c:29:9: warning: cast removes address space '<asn:2>' of expression
arch/powerpc/cpu/mpc8xx/micropatch_usb_sof.c:30:9: warning: cast removes address space '<asn:2>' of expression

This is because of (void *) casts for using memcpy() as a substitute.

Do like other architectures, __force the cast to silence the warning

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index 998a82a..f63cae0 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -95,9 +95,9 @@
 
 #define IO_SPACE_LIMIT ~0
 
-#define memset_io(a,b,c)       memset((void *)(a),(b),(c))
-#define memcpy_fromio(a,b,c)   memcpy((a),(void *)(b),(c))
-#define memcpy_toio(a,b,c)  memcpy((void *)(a),(b),(c))
+#define memset_io(a,b,c)       memset((void __force *)(a),(b),(c))
+#define memcpy_fromio(a,b,c)   memcpy((a),(void __force *)(b),(c))
+#define memcpy_toio(a,b,c)  memcpy((void __force *)(a),(b),(c))
 
 /*
  * Enforce In-order Execution of I/O: