x86/atom: use neg instead of not/inc

The x86 apparently has a dedicated instruction for
finding the 2's complement.

arch/x86/include/arch/atom.h

@@ -158,7 +158,7 @@ inline int atom_or(atom_t *atom, int val)
 
 	__asm__ volatile(
 "	movl	(%2),	%0	\n" /* eax = atom->_value */
-"1:	orl	%0,	%1	\n" /* eax |= eax */
+"1:	orl	%0,	%1	\n" /* val |= eax */
 "	lock			\n"
 "	cmpxchgl %1,	(%2)	\n" /* if (atom->_value == eax) atom->_value = eax */
 "	jne	1b		\n" /* else goto 1 (eax updated to new atom->_value) */

arch/x86/sys/atom.S

@@ -90,8 +90,7 @@ ASM_ENTRY(atom_sub)
 	mov	8(%ebp), %edx
 	mov	12(%ebp), %eax
 	/* there is no xsubl, so we add the two's complement */
-	not	%eax
-	inc	%eax
+	neg	%eax
 	lock
 	xaddl	%eax, (%edx)