libthread: rm OpenBSD tas implementations

OpenBSD is using pthreads now, so no need for tas.

src/libthread/OpenBSD-386-asm.s

@@ -1,10 +1,3 @@
-.globl _tas
-_tas:
-	movl $0xCAFEBABE, %eax
-	movl 4(%esp), %ecx
-	xchgl %eax, 0(%ecx)
-	ret
-
 .globl getmcontext
 getmcontext:
 	movl	4(%esp), %eax
@@ -17,7 +10,7 @@ getmcontext:
 	movl	%esi, 24(%eax)
 	movl	%ebp, 28(%eax)
 	movl	%ebx, 36(%eax)
-	movl	%edx, 40(%eax)		 
+	movl	%edx, 40(%eax)
 	movl	%ecx, 44(%eax)
 
 	movl	$1, 48(%eax)	/* %eax */

src/libthread/OpenBSD-power-asm.S

@@ -1,18 +1,3 @@
-ENTRY(_tas)
-	li	%r0, 0
-	mr	%r4, %r3
-	lis	%r5, 0xcafe
-	ori	%r5, %r5, 0xbabe
-1:
-	lwarx	%r3, %r0, %r4
-	cmpwi	%r3, 0
-	bne	2f
-	stwcx.	%r5, %r0, %r4
-	bne-	1b
-2:
-	sync
-	blr
-
 ENTRY(_getmcontext)				/* xxx: instruction scheduling */
 	mflr	%r0
 	mfcr	%r5