asm-generic: allow generic unaligned access if the arch supports it

Switch the default unaligned access method to 'hardware implemented'
if HAVE_EFFICIENT_UNALIGNED_ACCESS is set.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>

include/asm-generic/unaligned.h

@@ -4,22 +4,27 @@
 /*
  * This is the most generic implementation of unaligned accesses
  * and should work almost anywhere.
- *
- * If an architecture can handle unaligned accesses in hardware,
- * it may want to use the linux/unaligned/access_ok.h implementation
- * instead.
  */
 #include <asm/byteorder.h>
 
+/* Set by the arch if it can handle unaligned accesses in hardware. */
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+# include <linux/unaligned/access_ok.h>
+#endif
+
 #if defined(__LITTLE_ENDIAN)
-# include <linux/unaligned/le_struct.h>
-# include <linux/unaligned/be_byteshift.h>
+# ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+#  include <linux/unaligned/le_struct.h>
+#  include <linux/unaligned/be_byteshift.h>
+# endif
 # include <linux/unaligned/generic.h>
 # define get_unaligned	__get_unaligned_le
 # define put_unaligned	__put_unaligned_le
 #elif defined(__BIG_ENDIAN)
-# include <linux/unaligned/be_struct.h>
-# include <linux/unaligned/le_byteshift.h>
+# ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+#  include <linux/unaligned/be_struct.h>
+#  include <linux/unaligned/le_byteshift.h>
+# endif
 # include <linux/unaligned/generic.h>
 # define get_unaligned	__get_unaligned_be
 # define put_unaligned	__put_unaligned_be