lib: Add log2 ceiling function

Change-Id: Ifb41050e729a0ce314e4d4918e46f82bc7e16bed
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/4684
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/lib.h

@@ -28,6 +28,7 @@
 /* Defined in src/lib/clog2.c */
 unsigned long log2(unsigned long x);
 #endif
+unsigned long log2_ceil(unsigned long x);
 
 /* Defined in src/lib/lzma.c */
 unsigned long ulzma(unsigned char *src, unsigned char *dst);

src/lib/clog2.c

@@ -27,3 +27,18 @@ unsigned long log2(unsigned long x)
 
         return pow;
 }
+
+unsigned long log2_ceil(unsigned long x)
+{
+	unsigned long pow;
+
+	if (! x)
+		return -1;
+
+	pow = log2(x);
+
+	if (x > (1ULL << pow))
+		pow++;
+
+	return pow;
+}