lib: import bitrev library from the linux kernel

This patch adds the bitrev library from the linux kernel.  This is a simple
algorithm that uses an 8 bit look-up table to reverse the bits in data types of
8, 16, or 32 bit widths.  The docg4 nand flash driver uses it.

[port from linux kernel v3.9 commit 7ee32a6d30d1c8a3b7a07a6269da8f0a08662927]
[originally added: v2.6.20 by commit a5cfc1ec58a07074dacb6aa8c79eff864c966d12]

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
new file mode 100644
index 0000000..a61d956
--- /dev/null
+++ b/include/linux/bitrev.h
@@ -0,0 +1,23 @@
+/*
+ * This file is released under the terms of GPL v2 and any later version.
+ * See the file COPYING in the root directory of the source tree for details.
+ *
+ * Based on bitrev from the Linux kernel, by Akinobu Mita
+ */
+
+#ifndef _LINUX_BITREV_H
+#define _LINUX_BITREV_H
+
+#include <linux/types.h>
+
+extern u8 const byte_rev_table[256];
+
+static inline u8 bitrev8(u8 byte)
+{
+	return byte_rev_table[byte];
+}
+
+u16 bitrev16(u16 in);
+u32 bitrev32(u32 in);
+
+#endif /* _LINUX_BITREV_H */