Remove assembly coded log2 function

As we move to supporting other systems we need to get rid of assembly
where we can. The log2 function in src/lib is identical to the assembly
one (tested for all 32-bit signed integers :-) and takes about 10 ns
to run as opposed to 5ns for the non-portable assembly version. While speed
is good, I think we can spare the 15 ns or so we add to boot time
by using the C version only.

Change-Id: Icafa565eae282c85fa5fc01b3bd1f110cd9aaa91
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/1928
Tested-by: build bot (Jenkins)

src/arch/x86/include/bitops.h

@@ -1,20 +0,0 @@
-#ifndef I386_BITOPS_H
-#define I386_BITOPS_H
-
-/**
- * log2 - Find the truncated log base 2 of x
- */
-
-static inline unsigned long log2(unsigned long x)
-{
-	unsigned long r = 0;
-	__asm__(
-		"bsrl %1, %0\n\t"
-		"jnz 1f\n\t"
-		"movl $-1, %0\n\t"
-		"1:\n\t"
-		: "=r" (r) : "r" (x));
-	return r;
-
-}
-#endif /* I386_BITOPS_H */