x86: Add ilog2 to bitops

ilog2 is required by AHCI driver

Signed-off-by: Graeme Russ <graeme.russ@gmail.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index c7a38f2..5a7e4cb 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -351,6 +351,11 @@
 }
 #define PLATFORM_FFS
 
+static inline int __ilog2(unsigned int x)
+{
+	return generic_fls(x) - 1;
+}
+
 /**
  * hweightN - returns the hamming weight of a N-bit word
  * @x: the word to weigh