powerpc: Remove orphaned asm implementation of abs()

This has been unused since ~2004, remove it.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/misc_32.S

@@ -599,12 +599,6 @@ _GLOBAL(__bswapdi2)
 	mr      r4,r10
 	blr
 
-_GLOBAL(abs)
-	srawi	r4,r3,31
-	xor	r3,r3,r4
-	sub	r3,r3,r4
-	blr
-
 #ifdef CONFIG_SMP
 _GLOBAL(start_secondary_resume)
 	/* Reset stack */